kl 1W thflfllflll‘ IS ”MIMI! h I l 144 540 HTHS A MOMHOLOQECAL STUDY OF AN EYE ANOMAL‘! IN THE ALSENO gAT W955: {w {rho 99am cf M. S. ffiiCfi—flfl'fifi “A“??? COLLEGE gmmice Aivén Caraway WQS THesu§ This is to certifg that the thesis entitled A MOrphologicel Study Of An Eye Anomaly In The Albino Rat. presented bg Prentice A. Caraway has been accepted towards fulfillment of the requirements for 459‘, .54 -, degree inZGQlc-gy Major professor Datel‘éfié! 3353* ~_ _ iv—‘w — a—n—wn—Iwu’..n ,m w‘wr v I ".|l. A.HORPHOLOGICAL STUDY OF AN EYE ANOMALI IN THE ALBINO RAT By PRENTICE ALVIN 945mm A THESIS Submitted to the School of Graduate Studies of Michigan State College of Agriculture and Applied Science in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Department of Zoology 1948 THEiiS IN, ll). .ll."llllll"ll ltl’llr |.:l|' lit-II" llllt' It'll?! fill Introduction . . . . . . . . . . . . . . Materials and Methods Description 7 mm. . TABLE OF CONTENTS 9 mm. . . 12 mm. . . 18 mm. . . 21 mm. . . Discussion . Summary Literature Cited Plates {if} “4516): (Med! 3 of Developmental Stages page 1 2 (003901 10 12 16 17 21 \ l’. ll" ACKNOWLEDGEMENTS I am.greatly indebted to Dr. R.A. Fennell, Professor of Zoology, Michigan State College, for his careful guidance and many helpful suggestions during the entire study, and to Dr. J.H. Quisenberry, Head of the Department of Poultry Husbandry, The Agricultural and Mechanical College of Texas, ‘who suggested the problem.and furnished the animals used in this study. I express appreciation to Dr. H.R. Ennt, Head of the Department of Zoology, Michigan State College, for reading the manuscript. I extend thanks to my wife, Corrinne, for aid in preparation of the manuscript and to Bernadette Henderson for her many suggestions. To all others who havev given aid and encouragement, the writer extends his thanks and appreciation. A MORPHOLOGICAL STUDY OF AN EYE ANOMABY IN THE ALBINO RAT INTRODUCTION Two eye anomalies, anophthalmus and microphthalmus, in the albino rat were reported by King ('31). Opportunity, however, was not presented to continue the study embryologi- cally due to the death of the stock. Quisenberry and Brown (I42) report a similar anomaly and from this strain indi- viduals were selected for this study. Objectives were as follows: (1) to determine the morphological nature of the anomaly during stages of fetal growth; (2) to determine the fetal age of its occurrence and (3) to learn something of the nature of the factors causing the trait. MATERIAL AND METHODS A total of nineteen embryos from five pregnant rats were sectioned. The animals used were stock.individuals from the colony of the Texas Agricultural Experiment Station and the personal stock.of Dr. J. H. Quisenberry. The male was left with.the female from.6:00 P.M. until 8:00 A.M. and .matings were timed by the vaginal smear method. Long and Evans ('22) state that mating takes place in the early hours of stage two (oestrum). The timing of the embryos in these cases was accurate only to about twelve hours. Sizes of embryos were recorded from crown-rump (CIR) measurements in millimeters. Embryos were collected by anaesthetizing the pregnant female and removing the complete uterus and fetuses. Follow- ing removal of the embryos they were fixed in Bouints fluid and embedded in paraffin by use of the dioxan technique as reviewed by Mossman (tSV). Serial sections were cut at 10 microns, stained in Delafieldts hematoxylin, and counter- stained in eosin. Normal control animals were taken from a highly inbred strain that exhibited no similar eye defect. Embryos were prepared for examination.by identical methods as those used in preparation of anomalous individuals. riflrllrlllrll (ll [lllflilfilll I -3- DESCRIPTION OF DEVELOPMENTAL STAGES Sgyen.Millimeter Stgg_. Three anomalous embryos were obtained by mating a male (right eye anophthalmic, left eye normal) with a female (anophthalmic in both eyes). The maximum diameters exhibited by the optic cup and lens in the control were 420a? and 150u.respectively. A comparison.of the data presented in Table 1 shows that the diameter of the optic cup and lens vesicle in the anomalous embryos varied from.a minimum of 156u.and 95u to a maximum of 370a and lBOu respectively. It is also evident that there is significant difference between diameters of the optic vesicles and lens in right and left eyes of anomalous embryos. The left eye of E0701 was in the lens vesicle stage; the diameter of the optic cup and lens were 156u and 95a respectively. The optic cup consisted of two undifferentiated layers which were separated by a well defined optic ventricle (fig. 2). It was also evident that the lens vesicle consisted of a single layer of columnar epithelial cells and that the lumen was circular. The right eyes of E0701 and E0702 and the left eye of E0703 were approximately equal in size and exhibited striking similarities in degree of development. In all cases the lens structure was in the vesicle stage and closely resembled that of the control (fig. 1). * u : micron -4— Further, the distal portion of the optic vesicle had invaginated to reduce the cavity of the optic ventricle to a minimum. This inner layer displayed typical charac- teristics of the sensory layer similar to that in the control (fig. 1). The outer pigmented layer of the optic cup was very thin.and in close proximity to the sensory layer. The left eye of E0702 (fig. 8) and the right eye of E0703 (fig. 4) showed a degree of development very similar to that of the control. Both eyes exhibited a well differentiated sensory layer, pigmented layer, and lens vesicle. However, the lens vesicle of E0703 appeared to be further advanced due to the fact that the cells of the inner (proximal) wall had increased in height to produce a ''crescent" shaped lumen (L, fig. 4). Nine Millimeteregtgg_. Four anomalous embryos were ob- tained by mating a male (right eye anophthalmic, left eye normal) with a female (microphthalmic in both eyes). In the control the maximum size of the optic cup and lens were 650u.and 400u.respectively. The invagi- nated portion of the optic stalk was in contact with the pigment layer of the retina and the two layers of the cup‘were well differentiated into an inner nervous layer and a thin pigmented outer layer (fig. 5). The data in Tablelshow that in.the left eye of anomalous embryo E0901 the optic cup and lens vesicle exhibited -5- a maximum diameter of 280u.and l70u respectively. The optic cup consisted of two very thin layers essentially the same in thickness. The lens vesicle consisted of a single layer of columnar epithelial cells arranged to form a circular lumen (fig. 6) while the epithelium in the proximal wall of the lens in.the control (E0906) had elongated to such an extent as to almost obliterate the cavity of the original vesicle (fig. 5). In the control mesenchyme cells were present between the distal wall of the lens and superficial ectoderm, but in the anomalous embryo mesenchyme was absent and the two layers were in close contact (M, fig. 6). In general, the degree of development of the left eye of E0901 approximated that of five millimeter control series. The left eye of E0902, the right and left eyes of E0903, and the left eye of E0904 (fig. 9) were very similar in structural development and size to the above described left eye of E0901 (fig. 6). However, in the left eye of E0903 the distal wall of the optic vesicle had invaginated only to a slight degree (fig. 8). This condition exhibited an optic vesicle cavity which resembled those of a very early control series (3 mm.). Another interesting feature was exhibited in the left eye of E0904. The layers of the optic cup were of equal thickness but'were lying in.close proximity, in contrast to E0903 above. In.addition, the optic cup was folded or “crumpledu into a very irregular shape as shown in Fig. 9. The right eye of E0904 (fig. 10) and E0902 very closely approximated that of the control in structural development. However, the right eye of E0904 displayed a slightly larger gross size. Twelve Millimeter Stage. Four anomalous embryos were obtained by mating a male (right eye anophthalmic, left eye normal) with a female (anophthalmic in both eyes). Anomalous structures of the right and left eye of E1201 (fig. 11) were essentially the same as those present in both eyes of E1204, the right eye of E1202, and the left eye of E1203. It is evident from Fig. 11 that in E1201 the optic cup and lens vesicle were en- tirely absent. However, a small optic nerve extended from.the brain to the eye region where it terminated abruptly in a dense bundle of mesenchyme tissue (on, fig. 11). Further study of anophthalmic embryos in this series revealed that the degree of development of the eyelid primordia was greater than it was in normal eyes. The eyelids of normal embryos were not fused but in anophthalmic embryos fusion of the eyelids was complete. A study of the left eye of E1202 revealed a small lens vesicle and optic cup (fig. 12). The lens was in the early vesicle stage since the anterior and posterior walls were made up of a single layer of columnar cells. However, in control embryos of this age series cells of the inner wall of the lens vesicle had elongated to obliterate the cavity of the lens vesicle (fig. 14). The walls of the optic cup in anomalous embryo E1202 consisted of a single layer of thin columnar cells and there was no indication of differentiation into a nervous layer or pigmented region (fig. 12). Mesenchymal cells had completely invested the space between the lens vesi- cle and the optic cup. The right eye of E1203 ethibited several differences from those previously described. The size of the optic cup and lens approximated the normal eye in that the cavity of the lens vesicle was obliterated by the lengthening of the cells of the posterior wall. However, marked differences occurred in the arrangement of the lens fibers. This was especially evident in that the central lens fibers near the anterior epithelial layer were separated by large vacuoles (fig. 13). Lens fibers in the posterior (proximal) region of the lens were normally arranged. The optic stalk reached a maximum diameter of 30u in the optic foramen while the diameter of the optic stalk of the control at that point was 90u. In the normal eye a well defined nerve fiber layer covered the inner surface of the cup. These fibers con- verged and passed inward through the optic stalk. However, in the anomalous eye (E1203) a well defined nerve fiber layer existed but the convergence of fibers took place in the ventral region of the cup (fig. 13) instead of in that region immediately adjacent to the optic stalk. Eighteen.Millimeter St§g_, Five anomalous embryos were obtained by mating a male (both eyes anophthalmic) with a female (left eye anophthalmic, right eye microphthalmic). .Two embryos (E1802, E1805) displayed anophthalmia in both eyes. A comparison of the optic cup regions of these two embryos with that of an earlier embryo exhibiting anophthalmia in both eyes (E1201) showed that the two age groups differed in several respects. In E1201 the optic cup region of both eyes exhibited a small optic nerve (fig. 11) invested by a relatively heavy layer of mesoderm but in E1802 and E1805 both of these structures were absent. The latter embryos displayed anotherinteresting feature. A crescent shaped mass of cells, essentially the same cyto- logically as those at the Junction of the eyelids, was found in contact with the inner surface of the lids. The'writer is led to believe that this crescent shaped mass of cells developed from an inpocketing of marginal epithelium found at the point of contact between the upper and lower lids. A review of the data given in Table 1 shows that the degree of development in the right and left eyes of E1801 and the left eye of E1803 (fig. 18), 18 mm. embryos, and the left eye of E1202, 12 mm. embryo, is essentially the same since the diameters of both lens and optic cup in the 18 mm. embryos approximates that found in the left eye of the 12 mm. embryo. It was brought out in the pre- ceding pages that in E1202 (fig. 12) the lens was in the vesicle stage and that the optic cup was made up of two undifferentiated layers. The chief difference between -9- the lens vesicle of the left eye of E1202 (fig. 12) and E1801 was that the epithelium of the former consisted of a single layer of short columnar cells while in the latter the epithelium had obliterated the lumen of the vesicle.. The left eye of E1804 (fig. 16) exhibited very similar conditions to those described above except for lens structure. in epithelial layer of loosely arranged columnar calls made up the wall of the spherical lens. The lumen of the lens vesicle was filled with poorly developed or degenerated lens fibers sharply separated from the epithelial layer. Several vacuoles were present between these fiber-like structures and the columnar cells. The right eyes of E1803 (fig. 17) and E1804 showed striking similarities in structural development. However, the gross size of E1804 approximated that of the control in contrast to E1803 which.was approximately one-half that “of the control. Indication of cornea formation (fig. 17) was shown in both eyes by invasion of mesoderm ‘cells between.the epithelial layer of the lens and the superficial ectoderm.covering the eye. The lens displayed considerable deviation from those of the control. The lens fibers in the proliferative zones appeared normally arranged and growth of the lens fibers from the posterior ‘wall gave the appearance of’a normally developed half of the lens. The anterior (distal) half of the lens was filled with very large vacuoles (fig. 17). -10- Egggty-one Millimeter St§g_. Three anomalous embryos 'were obtained by mating a male (both eyes anophthalmic) ‘with a female (both eyes anophthalmic). The data given in Table 1 show that one embryo (E2102) was anophthalmic in the left eye and microphthalmic in the right eye. All others were microphthalmic in both eyes. Optic cup and lens structures were entirely absent in the left eye of E2102 (fig. 20). A very similar condition was noted in the left eye of E1201 in the twelve millimeter series (fig. 11). The size of the lens and optic cup in the remaining embryos varied from 290u to 180u and from 400u to 200u.respectively. Very similar conditions have been de- scribed for E1801 and E1803 (fig. 18) in the eighteen millimeter series and E1202 (fig. 12) in.the twelve milli- meter series. However, the lens of E2102 and E2103 exhibited a more advanced stage of epithelial proliferation and as a consequence the lumen was almost obliterated. In addition, these elongated lens fibers were irregularily arranged within the lumen and were separated by numerous large vacuoles (fig. 19). -11- owe ovoadnoymmo moHOfiE I a u_.. "as 8mm 8mm 8mm 8mm .5 a ma moan sow.” 90mm amount amount .aa .8 w." NOHNM 88. soon 8E 80: .E a 3 same :83 zoomm .E a ma moan amomno phonon panned amoeba .aa ma ma mowdw 88H :89 sown some .as we 3 En 82. :83 some seem as we 3 03m. amount amoeba amoeba amoeba .5 ma w.” momdm comm zoom noma sown .25 we we Homes nomad zooma .as we we momam Pnompu #nomnw abound abound .5 NH .5” MONHH. soon zoom sponge anonen .as NH ea omen amoeba poompo some 8mm .6: ma 2." «ONE.» . anomnm gonna amoeba gonna .86 NH 1.? Homaw zoom .58 .5: NH i momma 8am 8mm. no: snow .as m D mom 85 some 83 8mm .5 m D 08» 8m. 98m :09 some .5 m D momom some 891 SS 8mm .3: m 3 88m 58: some .as m ma women .53 8mm :3 use .2 a 2 mace . 89 zoom 83 8R .5 a. «H moaoe .63 8%. 9mm 69 .as a NH Home some A Vsome .aa a NH moaom a nooosoae nooosoao noooaoae nooosoae one.“ one 330 33 Q6 33o 93883 .3908ch m\o 1.93“. 9352 one “Emma the to." 33.. 9.5 0.390 .owd. 30.3805. H9350 eczema he 533.839 mpmm 2:93. 5" ogmnpnmog one mgmnpnmehogw H Sea. DISCUSSION It has been shown in preceding pages that in the anomalous embryos optic cup development was always ac- companied by development of a lens. In those embryos (E1201, E1202, E1203, E1802, E1805 and E2102) in which one, or both, optic cups failed to develop, there was no indication of lens development. These observations suggest that the lens may be induced by the optic cup. Induction of the lens in lower vertebrates has been ablely investigated by several workers. In certain amphibians Lewis ('07), Stockard ('07), and others, have shown that the formation of the lens depends di- rectly upon the stimulation of the ectoderm by contact ‘with the optic vesicle. Further, Lewis ('07) states: ”the size of the early lens-structure is due in part to the area of contact or adhesion between optic vesi- cle and ectoderm, and in part to the length of time the optic vesicle or optic cup remains in contact by its retinal layers with the growing 1ens-structure.'I Le Cron ('07) augmented this by illustrating that the lens in Amblystoma punctatum was not self-differentiating but depended upon the continued influence of the optic cup for its normal development. Eigenman ('98) found that a lens structure was present in young embryos of Amblyopsis (a blind cave fish) but completely absent in old embryos. Stockard ('07), in his study of embryos of blind cave fish (Bdellostoma stouti), showed that -13... "the optic-vesicle may change into an optic-cup without the aid of the mechanical pressure of the lens." However, all anomalous embryos in this study that exhibited an optic cup, irrespective of the size, also displayed a lens. Spemann ('12) reported that the lens was capable of development in.some amphibians without the stimulus of an optic vesicle. This controversial "lens-problem" is discussed by werber ('18). Again, this series of a- nomalous embryos displayed no evidence of a lens present without the optic cup. It has been illustrated in previous pages that expression of this anomaly varied from.comp1ete anoph- thalmia to near normal size eye. Eigenmann ('98, '99, '01) made extensive investigations on blind vertebrates and found that the degree of anomaly varied greatly. As to causes of this variation, he believes that development ceases at some ontogenetic stage and this is followed by a degeneration which is a continuous reduction of organs of the eye to the adult stage. In this study indications of degeneration of eye structures, especially the lens, were exhibited in several embryos (E1203, E1803, E1804, E1805, and E2101). Size of the lens ranged from near normal to microphthalmic; however, conspicuous vacuoles were present in.a11 of the lenses as illustrated in figs. 13, 16, 17, and 19. The distal portion of the right lens of E1203 and E1803 presented extreme irregularity in arrangement of lens fibers. In addition, E1203 showed -14.. evidence of shrinkage of the distal surface of the lens adjacent the heavily vacuolated area (fig. 13). In contrast to Eigenmann's views, Stockard ('21) has presented the hypothesis that during embryogeny the faster growing regions are more inhibited by adverse conditions than the slower growing ones. In a study of anophthalmic mice, Chase and Chase ('42) concluded that after the optic vesicle formed there was an inhibition of the growth of the vesicle. The seven.millimeter series of this study exhibited no major absences of structures; however, the gross sizes of these structures, in general, were less than those of the control. Individuals that exhibited microph~ thalmic eyes presented levels of development comparable to a much earlier embryo (five millimeter control). The nine millimeter stage revealed no anophthalmic eyes but exhibited a wide range in.gross size of structures. Again, the size of the optic cups and lens vesicles of five of the eyes of this series appeared no further advanced than the five millimeter control stage. Similarly, the twelve millimeter, eighteen.millimeter, and twenty-one millimeter groups presented microphthalmic eyes that exhibited a stage of development closely approximating that of five milli- meter control series. The observations made in this study33uggest that microphthalmic and anophthalmic eyes might be due to a factor (or factors) which inhibit early development rather than to a secondary degeneration or absorption of eye structures at some time after the onset -15... of development. In a study of fowl (homozygous Creeper) embryos, Landauer ('32) concluded that no sharp line could be drawn between the (facts of extreme retardation and a complete inhibition of later development. He states: “The homozygous Creeper condition appears to be expressed chiefly by a retardation of growth in general but at a time when the extremities and the head are most susceptible to such.influences." Another interesting feature was noted in E0904. The optic cup was collapsed and folded as shown in Fig. 9. Beckwith ('27) states that "in all the eyes of Amblystoma punctatum in which the lens was not present the optic cup ‘was variously folded or collapsed and the vitreous humor was absent." Hewever, in E0904 a very small lBDS‘IES present. Twitty ('32) found that "following embryonic extir- pation of the eye, the muscles fail to develop their typical arrangement. In extreme cases they may become condensed into a single mass so that their individual identity is obscured.u In this study all embryos that exhibited complete anophthalmia revealed no ocular muscles. -16.. SUMMARY 1. Degrees of expression in the anomalous strain ranged from.comp1ete anophthalmia in both eyes to both eyes near normal size. The highly inbred control strain gave all normal sized eyes. 2. Embryology and gross morphology of the anomaly are presented. Timed matings were utilized to obtain embryos in the two strains, and the eye regions were compared. 3. Optic cup development was always accompanied by development of a lens.~ No specimen showed lens development in the absence of an optic cup. 4. observations suggest that there is an inhibition of growth in the early developmental stages rather than a degeneration or absorption of eye structures in the more advanced age groups of embryos. 5. Anophthalmic eyes revealed no ocular muscles. -17... LITERATURE CITED Beckwith, Cora J. 1927 The effect of the extirpation of the lens rudiment on the development of the eye in Amblystoma punctatum, with.special reference to the choroid fissure. J. Exp. 2001., vol. 49, pp. 217-259. Chase, H. B. and E. B. Chase 1942 Studies on an anophthalmic strain of mice. I. Embryology of the eye region. .Jour. morph., vol. 68, PP. 279- 301. Eigenmann, C. H. 1898 Degeneration in the eyes of Amblyopsidae, its plan, process and causes. Proc. Indiana Acad. Sci., 1898, pp. 239-241. Eigenmann, C. H. 1899 Degeneration in the eyes of the cold-blooded vertebrates of the North American caves. Proc. Indiana Acad. Sci., 1899, pp. 31-46. Eigenmann, C. H. 1901 The eye of Rhineura floridana. Proc. Indiana Acad. Sci., 1901, PP. 106-107. -18... King, Helen D. 1931 Studies on the inheritance of structural anomalies in the rat. Am. J. Anat., vol. 48, pp. 231-260. Landauer, l. 1932 Studies on the creeper fowl. III. The early development and lethal expression of homozygous creeper embryos. J. Gen. vol. 25, PD 0 367‘394 0 Le Cron,‘!. L. 1907 Experiments on the origin and differentiation of the lens in Amblystoma. Am. J. Anat., vol. 6, pp. 245-257. Lewis, W. H. 1907 Experimental studies on the development of the eye in Amphibia. III. 0n the origin and differentiation of the lens. Am. J. Anat., vol. 6, PP. 473-509. Long, J. A. and H. M. Evans 1922 The oestrous cycle in the rat and its associated phenomena. Hem. uni-V. Of Cale, V01. 6’ pp. 1-148. -19.. Mossman, H. W. 1937 The dioxan technic. Stain TeCh.’ V01. 12’ pp. 147‘1560 Quisenberry, J. H. and S. 0. Brown 1942 Inheritance of an eye anomaly in the albino rat. Genetics, vol. 27(1), pp. 162-163. Spemann, H. 1912 Zur Entwicklung des Wirbeltierauges. Zool. Jahrb. Abt. Allg. Zool. u Phys., vol. 32, pp. 1‘98 . Stockard, C. R. 1907 The embryonic history of the lens in Bdellostoma stouti in relation to recent experiments. Am. J. Anat., vol. 6, pp. 511-515. Stockard, C. R. 1921 Developmental rate and structural expression. Am. J. Anat., vol. 28, pp. 115- 277. Twitty, V. C. 1932 Influence of eye on growth of its associated structures, studied by means of hetero- plastic transplantation. J. Exp. Zool., vol. 61, pp. 333-374. -20- lerber, E. I. 1918 Critical notes on the present status of the lens-problem. Biol. Bull., vol. 34’ pp 0 219‘249 e PLATES OEOO?‘ O PLATE I Explanation of Figures Left eye region of 7mm. control embryo (E0706). Frontal section through lens vesicle and optic cup. The two layers of the optic cup are differentiated into an outer, thinner (pigment) layer and an internal, thicker (nervous) layer. x 172. Left eye region of 7mm. anomalous embryo (E0701) showing the two layers of the optic cup of equal thickness and separated by a well defined optic ventrfcle. x 172. KEY TO PLATES V, lens vesicle V, vacuole N, optic nerve L, lumen C, optic cup S, sensory layer of optic cup F, lens fibers P, pigment layer of optic cup 0' folded layers of M, lens and superficial optic cup ectoderm in close contact V, optic ventricle C, cornea L, eye lid F, nerve fibers , ww\&Wfi 10-. w . it“s *3. _ ‘ . ’ .. .v at. a o. d» I a a a..." . t. “\Qt . . a . ‘ 4‘ 6.- .. a t . 3 . I. A .s x «I . -lnbnhl ' JL .0 A... «1‘ \o0'4. PLATE II Explanation of Figures 3 Left eye of 7mm. anomalous embryo (E0702) showing a degree of development very similar to that of the control. x 172. 4 Right eye of 7mm. anomalous embryo (E0703). The "crescent" shaped lumen of the lens vesicle can be seen. x 172. . .71. r .11.» aft; .1 . .L ---_ - t .- \- a. x a . I ‘ PM. 5. ...‘3 'I ~\ \. PLATE III Explanation of Figures 5 Left eye of 9mm. control embryo (E0906). The inner layer of the optic cup is much.thickened and the lumen of the lens vesicle is virtually eliminated. x 172. 6 Left eye of 9mm. anomalous embryo (E0901). The lens vesicle (L V) consists of a single layer of columnar cells which form a circular lumen. The distal wall of the lens vesicle and superficial ectoderm.are in close contact at M. x 172. use C’- . .. . k l O I - v . in. .. l u. u e . u ‘ f .s. w _ ... cl...” . a . .4 u JV. . p e O I: . . a. . . “... on. . .. o . I, .o \. . c. I .. A V t . . ‘ U . L c o. . v o w 6. ... o _ ......» a «hub... e... . l\ . .. . t0 ’ eh” .u .S b V . . . . V “o e.. .2 ‘ o . v. - I . \ M. Q n '..u.‘fv‘tll_ ‘- . ..D. t... u. 1.... .l ‘ ‘3 I k V V - . . s t . b . . v ‘ I v 2. . .av . ... . I a ftn . § . . a PLATE IV Explanation of Figures 7 Right eye of 9mm. anomalous embryo (E0901). x 172. 8 Left eye of 9mm. anomalous embryo (E0903). The slightly invaginated optic vesicle can be seen. x 172, PLATE V Explanation of Figures 9 Left eye of 9mm. anomalous embryo (E0904) showing extreme folding of the optic cup (00'). x 172. 10 Right eye of 9mm anomalous embryo (E0904). The sensory layer (S) and the pigment layer (P) exhibit degrees of development similar to those of the control. 1 172. PLATE VI Explanation of Figures 11 Left eye of 12mm. anomalous embryo (E1201). Optic cup and lens vesicle structures are entirely absent. However, the fibers of the small optic nerve (0N) can be seen. x 172. 12 Left eye of 12mm. anomalous embryo (E1202). The small optic cup (0C) and lens vesicle can be seen. Mesenchymal cells invest the space between the lens vesicle and the optic cup. 1172, I . I .. . .n o . I n I I 4. .5. v 0’ o. 3. .e c . o . . J I . I '— ‘ A C I .w ' _ . . . . _ ; . . . ... .. .. . . . II. . . a . .l .. ct. .. v I. . . I . I. I .o . a. . n o . . .. . Q o n n.1- I I. o 4 I ..v . o In“. . It . em to. u ......I Frau. . . . . I V . I , t . er. . .I A.. .. .I N b . er. ' ...Iv\-\rv vI\ . . b . I v . \e I I . . TCAVN. .e.¢, 5" I . Hp . b: a. , I . .3 ._ -. a: .. .. m... ..I. .I ....n .... ...... . r . a Hal-JAV. h a _. .. . ~.nntt.a.\..,fi.awchnv ...U .35.... in a .39. .. o . ..t. via ...» Is: .7...” .. :2. t .. .iwI v . .I ... fltffié... ‘. I. I I \I 3.... ...? «......I... .... ...... .. . |I . III v.?. I. ... . . . . . H.101... to?” t... . .3 .l.. “gnaw”. 4.1. V .k . . a . - ..- . .I I .-. ... . I. a _ . am I... II..5A ..ItI‘?JI.e.a’ ._ DAWN...“ tmOIVl I; .U—qloel.‘ 00—1 Yr‘ .34.. 7:75. . . .I.v .... . a3. . o . ....tJ...-.n...a.. .I x... ........t.. v3.3.8: . .I . . . . .vi I ho I. .. ..e. )‘urfrsffin I I .l. ...... .. III... . .. . -. ... . .. .1"..# .... .9. . .. ... ... ., ..1 .. .. I . . It .... _ .. ......1 . . . . . . I‘JU‘.’ vTII 4w I)... J” ¥Ha .. L a“ J! l . .... ...;I. .....I.....m..v.{e}...... _ . . I. . .I . . . .t 33 m .. .... 5.3 a}, I. . . a . 4 I. .‘f .a o t . I... \- Xv I. :IV or. A I and“. _ RI“. .0;% ‘.~... e . . 5 I . r C~ a .e. S. a. o ‘1 v Ii. .( I _I . u 39h“. I 9.. n . . I e.~:au.n we. v . A \‘o‘fl . . t. . ...m ... lsvux an . «III. A , .. VIIAIvr .0 fl {\hv .l. . . t» I . .lhwlu...t .k‘. . . I? . v . .- ... s to? .. I. I t... L. 5:... oat I .I .... I It $32730. 2...... .... . .Mos... .vk.wn .... .... . . . t ... ... Ivar ....-. ....Ia..- a I . .. e. I.-. .5 1 o M‘ .H‘.. A. b t . . \“a ‘.M. ‘ .v..anh It Aw“. ..‘I AI 35.. I, $76.“.45 er .. . .... ... ”a ., .14.- Ihnek . I ... . .. u .I .0 . .r at o x . Io . .... I .4.. entv. . .r ... .I. .1 4 .w: . ....ur ......Q. .. ...LAI... ... m .1... ... - .v N . _. a ‘. . l I .o . I o... . to.“ .3 l 1'. .. 1.. . t o . o . —.I.. ’I. If.“ wu—w. ...-e v . _ O . I . I. v ... v \. Bdflfirot D,\A.\Wllw It v . . I. . . I I .... 15%;... at . I. . ~ Ir. 3.. . o r I a P o... .I V.N.lq I. . vi . I I . . . at Ihw 'l e . . I . . . . , Iv u. I It . e “me- .H. a . v .J%. o ”HQHOI. . I L . . ”upkhfluuouw . .. . a . ..l.. ‘ ...v . v w. I ...l I ... I! . . ...- . a... . .I I. .... . I . . . I 2%. . ......x .I .. in . . .o\ .vI e or...) . .I .. . h ....J...owv s. I .m .....C. .. . .- .ov v . .\¢QI...| N v . . a. t J..Io.. t-II . . . . . . s . ...: . . a. o . I. . o v I 0* v’awu‘ on... . .0 y.» I . a I 1.. W}: I. a _. I: I. ..,...I_.n.‘. r. ...J- . ..m .uo.tn ......I. fit. . I . .. .\.hoo . . A: .e. ... t 0' PLATE VII Explanation of Figures 13 Right eye of 12mm. anomalous embryo (E1203). Conspicuous vacuoles (V) fill the distal half of the lens. Nerve fibers converge at a point (F) in the ventral region of the sensory layer. x 172. 14 Right eye of 12mm. control embryo (E1206). 1 70. f. I. .. ...: . r '.O . I. . a.“ x 2. .. I in ‘ (I ' III. . I». . . v... 4 Cl ,a ... . ..A a. r. «an-II r0~.ofin . ... ... .. .4 .I 5 I .. x 6.... ......‘.U0v.£- In. . .. . .3: - I....... ...... “ ”kt IP11: ... a, (I . ..u..I . . .... r: In. ......I. . Q . Q, . IL' ...J. ..I 1.}. . I . .. I r; .. .. ......" .uv.....u..~V 15.... . .I I t I ..hh.v‘ . I. r} . . I u I .-.... I}? .. I. m... . - . a $3». .- fir. . r I .. . . . :- I ...-s r a A . ..4 1.\ _ ... ~ .s .o O .. .r. .. . u... . .ou . 4 . iv 1 AP. a). e n .f. .tv .0 t a. I... .. . . r h . _ .II \. .... I . . .11.... I. . .. . A . . \ L . ..n. v. .. . .. . :1... .. - .. s. .‘.L.v .. 1-. I . .. his: . .v.. I. .. . ..I u .d ‘ .I. . ~ I .VDII. v . PLATE VIII Explanation of Figures 15 Right eye of 18mm. control embryo (E1806). x 70. 16 Left eye of 18mm. anomalous embryo (E1804). Disarranged lens fibers (HF) fill the lens vesicle. x 70. *— ‘ If.“ . a. '31 'r ‘4- 'o “ .‘ q \ .Q \~ ooh}. t”; ' . L. PLATE IX Explanation of Figures 17 Right eye of 18mm. anomalous embryo (E1803). The distal portion of the lens exhibits extreme vacuolization. x 70. 18 Left eye of 18mm. anomalous embryo (E1803). x 172. v 1 I . ' ‘ l .- ‘31 . . a ‘J' . -‘ f’ . J .l o . . . - A v ' 1h]. - - _g. .‘ . . A ' _ " I § _ 4‘, ‘3‘ ~‘ k .. I .7.“ .7}, ‘ 'y.‘ . v v o a I ~ . ‘I "vi?! ’ 3 K" . “(1‘35 ’. ."."?~.-. ' V“ ‘ "at ‘ . w 1: L. ‘t. " 2: 73¢:‘r . Q “ 1“" . 2L3“; . ‘ . ‘ ' '. . I3 no _ .23; n, H .‘ fi 1 n...,_. , 4 r w . ._ J”, o f'. ...- . h 1% ‘3’? r- - I; ~ “"\"k: I ‘ k .d I h - z . b ‘ :1! I. 5’" _ ‘ L ‘1 . L. ..‘V' "I w'i‘ V ... . .‘SJ' ~ .. . .' p ‘5'. ‘ ,‘2 , o w. ”£1 -‘- "' J ? k. .‘ Q. ’ " _'... '0 ' I -- ‘ eii' L' l 3.- f .0 ' 't 4.9 .... . 0 ‘I In. cu . PLATE x Explanation of Figures 19 Left eye of 21mm. anomalous embryo (E2101). Numerous vacuoles (V) are present within the lens vesicle. x 172. 20 Left eye of 21mm. anomalous embryo (E2102). Optic cup and lens vesicle structures are absent; however, an extremely small optic nerve (OR) is present. x 172. \ . t v *" r [43”). y ‘4} 39111;. 5 fix. I.” . t‘ w A, ’1‘ . ,5 .. \ t: s.‘ I A I -‘ r4 / ~ 1 ‘J D “.1 ‘r i I" ;, J.‘ ”v k. \. '1'7,‘"'v'.' K'J'» ‘ . I ‘ ‘. ,‘Vb—' .f“ \ ‘a ‘ Vat. . u, . 1 r .‘ ‘ «A \ \ . v‘w ‘ R60??? USE ONLY .M‘ < F'g ’ . r I-.' 7 \ .C araway MICHIGAN STATE UNIVERSITY LIBRARIES llllllllllllll 3 1193 03082 6196