EXPLANATION OP' PLATE 26. 



Fig. 21. Ovum from the ovary of a half-grown female, containing isolated deeply 

 stained patches of developing yolk granules. Zeiss B, ocul. 2. Pkrk acid. 



Fig. 22. Section through a small part of the ovum of an immature female of 

 Scyllium cankula, to shew the constitution of the yolk, the follicular epithelium, and 

 the egg membranes. Zeiss E, ocul. 3. Chromic acid. 



Fig. 23. Section through part of the periphery of a nearly ripe ovum of Scy. 

 canicula. Zeiss C, ocul. 2. It shews the remnant of the vitelline membrane {v. /.) 

 separating the columnar but delicate cells of the follicular epithelium (/ e.) from the 

 yolk {yk.). In the yolk are seen yolk-spherules in a protoplasmic network. The 

 transverse markings in the yolk-spherules have been made oblique by the artist. 



Fig. 24. Fully formed ovum containing a second nucleus (x), probably about to 

 be employed as pabulum; from the same ovary as fig. 5. The follicular epithelium is 

 much thicker on the side adjoining the stroma than on the upper side of the ovum. 

 Zeiss F, ocul. 2. Osmic acid. 



Fig. 25. A. Ovum from the same ovary as fig. 21, containing in the yolk three 

 peculiar bodies, similar in appearance to the two small bodies in the germinal vesicle. 

 B. Germinal vesicle of a large ovum from the same ovary, containing a body of a 

 strikingly similar appearance to those in the body of the ovum in A. Zeiss E, ocul. 2. 

 Picric acid. 



Fig. 26. Section of the ovary of a young female o{ Scyllium stcllarc i61 centime- 

 tres in length. The ovary is exceptional, on account of the large size of the stroma 

 ingrowths into the epithelium. Zeiss C, ocul. 2. Osmic acid. 



Fig. 27. Ovum oi Scyllium canicula, 5 mm. in diameter, treated with osmic acid. 

 The figure illustrates the development of the yolk and a peculiar mode of prolifera- 

 tion of the germinal spots. Zeiss A, ocul. 2. 



Fig. 28. Small part of the follicular epithelium and egg membranes of a some- 

 what larger ovum oi Scyllium canicula than fig. 22. Zeiss D D, ocul. 2. 



Fig. 29. The same parts as in fig. 28, from a still larger ovum. Zeiss D D, 

 ocul. 2. 



Fig. 30. Ovum of Raja with follicular epithelium. Zeiss C, ocul. 2, 



Fig. 31. Small portion of a larger ovum of Raja than fig. 30. Zeiss DD, 

 ocul. 2. 



Fig. 32. Follicular epithelium, &c., from an ovum of Raja still larger than fig. 31. 

 Zeiss D D, ocul. 2. 



Fig. 33. Surface view of follicular epithelium from an ovum of Raja of about the 

 same age as fig. 32. 



Fig. 34. Vertical section through the superficial part of an ovary of an adult Raja 

 to shew the relation of the pseudo-epithelium to the subjacent struma. Zeiss DD, 

 ocul. 2. 



Plate 26. 



Complete List of Reference Letters. 



do. Developing ovum. fc. Cells which will form the follicular epithelium. /<■. 



Follicular epithelium, g c. C.erminal epithelium, mg: Malpighian boily. 11. Nest of 



cells of the germinal c-piihcliuni. 11 J. Nuclei in the act ..f dividing. 0. Permanent 



