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 of _Scyllium stellare_ 16-1/2 centimetres 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 of _Scyllium canicula_, 5 mm. in diameter, treated with osmic acid. The figure illustrates the development of the yolk and a peculiar mode of proliferation of the germinal spots. Zeiss A, ocul. 2. Fig. 28. Small part of the follicular epithelium and egg membranes of a somewhat larger ovum of _Scyllium canicul_a 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 D D, 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. 33. 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 stroma. Zeiss D D, ocul. 2. PLATE 26. COMPLETE LIST OF REFERENCE LETTERS. _do._ Developing ovum. _fc._ Cells which will form the follicular epithelium, _fe._ Follicular epithelium. _ge._ Germinal epithelium. _mg._ Malpighian body. _n._ Nest of cells of the germinal epithelium. _nd._ Nuclei in the act of dividing. _o._ Permanent ovum. _ov._ Ovary. _po._ Primitive ovum. _t._ Tubuliferous tissue, derived from Malpighian bodies. Fig. 35. Transverse section through the ovary of an embryo rabbit of eighteen days, hardened in osmic acid. The colours employed are intended to render clear the distinction between the germinal epithelium (_ge._) and the tubuliferous tissue (_t._), which has grown in from the Wolffian body, and which gives rise in the male to parts of the tubuli seminiferi. Zeiss A, ocul. 2. Fig. 35A. Transverse section through a small part of the ovary of an embryo from the same female as fig. 35, hardened in picric acid, shewing the relation of the germinal epithelium to the subjacent tissue. Zeiss D D, ocul. 2.