172 Wn-LTAM WALLACE. 



permanent ova developing in a single nest. In fig. 3 an 

 ovum, further advanced, is showu. There can have been no 

 extensive fusion here, since the permanent ova are still very 

 small, while the outlines of the surplus oogonia are quite 

 sharp and distinct. There was, however, frequently seen a 

 fusion of oogonia with developing oocytes at a still earlier 

 stage than that figured, before the formation of the follicular 

 epithelium, and it is highly probable that the ovum passes 

 through a sort of amoeba stage, during which it ingests 

 neighbouring oogonia, and grows in size at their expense. 

 There was also observed a breaking down and fusion together 

 of surplus oogonia in a nest to form a deeply staining granu- 

 lar mass, in which the original constituents are more or less 

 entirely obliterated. Degenerate masses of this nature were 

 sometimes, but not always, seen on the outside of a develop- 

 ing oocyte, somewhat flattened out between the latter and 

 the epithelium. Sometimes, then, if not always, the unsuc- 

 cessful oogonia go to the ground. 



As to the nourishment of the developing oocyte, it seems 

 probable after a very brief amoeba stage is passed thi'ougli, 

 that this is supplied by the lymph through the follicular 

 cells. As we have seen, the follicular epithelium is very 

 early formed around the oocyte (fig. 2), and the success- 

 ful ovum commonly occupies the deepest position in a nest 

 (fig. 3) nearest the source of nutriment. Soon, by the dis- 

 appearance of the unsuccessful oogonia, the oocyte comes 

 to be surrounded on all sides but the outside by a lymph 

 space, from which it is separated only by the follicular 

 epithelium and a single layer of endothelium. A theca 

 folliculi with blood-vessels is not formed until considerably 

 later. 



The above-recorded observations do not altogether bear 

 out the views of Jungersen (1889), who has studied the origin 

 of the ova in Zoarces and other forms. Jungersen found 

 sex cells already differentiated in embryos of Zoarces 2 mm. 

 long in which the blastopore was still open. He, and also 

 Eigenmann (189G), have discarded tlie old notion of a 



