OF THE VERTEBRATE OVARY. 603 



In other instances, which, so far as I can judge, are more 

 common than in the previous stages, the protoplasm of two or 

 more ova is fused together. 



Examples of this are represented in PI. 26, fig. 40 A. In 

 some of these the nuclei in the undivided protoplasm are all of 

 about the same size and distinctness, and probably the proto- 

 plasm eventually becomes divided up into as many ova as 

 nuclei ; in other cases, however, one or two nuclei clearly pre- 

 ponderate over the others, and the smaller nuclei are indistinct 

 and hazy in outline. In these latter cases I have satisfied my- 

 self as completely as in the case of Elasmobranchs, that only 

 one or two ova (according to the number of distinct nuclei) will 

 develop out of the polynuclear mass, and that the other nuclei 

 atrophy, and the material of which they were composed serves 

 as the nutriment for the ova which complete their development. 

 This does not, of course, imply that the ova so formed have 

 a value other than that of a single cell, any more than the 

 development of a single embryo out of the many in one egg 

 capsule implies that the embryo so developing is a compound 

 organism. 



In the innermost layer of the germinal epithelium the out- 

 lines of the original large nests are still visible, but many of the 

 follicles have been cut off by ingrowths of stroma. In the still 

 intact nests the formation of the follicles out of the cells of the 

 germinal epithelium may be followed with great advantage. 

 The cells of the follicle, though less columnar than was the case 

 at an earlier period, are more so than in the case of follicles 

 formed in the succeeding stages. The previous inequality in 

 the cells of the follicles is no longer present. 



The tubuliferous tissue in the zona vasculosa appears to me 

 to have rather increased in quantity than the reverse; and is 

 formed of numerous solid columns or oval masses of cells, 

 separated by strands of connective tissue, with typical spindle 

 nuclei. 



It is partially intelligible to me how Dr Foulis might from 

 an examination of the stages similar to this, conclude that the 

 follicle cells were derived from the stroma ; but even at this 

 stage the position of the cells which will form the follicular epi- 

 thelium, their passage by a series of gradations into obvious 



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