132 ZOOLOGY 



elusions will be found in most of Nath's papers on oogenesis 

 (93-102). 



The case of Ciona intestinalis , also investigated by two workers, 

 requires a certain amount of notice. Hirschler (49) derives yolk 

 granules from the mitochondria, and finds that vitellogenesis is 

 completed by a fusion of these granules with the Golgi bodies. 

 The mitochondria themselves are derived from the original yolk 

 nucleus which appears as a granule in the very early oocyte. 

 Harvey (45) also states that the mitochondria swell up to form the 

 ultimate yolk spheres of the mature ovum. The process described 

 is however very different from that stated by Hirschler. The 

 mitochondria are not derived from the yolk nucleus, being found 

 present together with it at the very earliest stage. The swelling 

 of the mitochondria comes about by the compounding by the 

 mitochondria of albuminous material in the form of the " yolk 

 nucleus " (secreted by the Golgi apparatus) and of lipoid material 

 contributed by the test cells, into the yolk spheres of the late 

 oocyte. Harvey is quite clear that he thinks that although the 

 mitochondria take an intimate part in the formation of the yolk, 

 they do not lose their identity as definite cell inclusions. 



In concluding a resume of our knowledge of the function of the 

 mitochondria in oogenesis, it is necessary to mention one or two 

 significant features. Firstly the two cases of Lumbricus and Ciona 

 are not incompatible. For this very good reason : we had 

 occasion to point out that the evolutions of the mitochondria 

 during spermatoteleosis were undoubtedly significant of something 

 but that it was impossible to say exactly of what. The same 

 applies here in the case of oogenesis. The complicated formation 

 known as the yolk nucleus followed by the spreading out of the 

 mitochondria must be of some importance. So far no facts have 

 been brought forward which completely bar the possibility that 

 the mitochondria are employed either directly or indirectly in 

 vitellogenesis. 



In conclusion then, the only progress made in connection with 

 the mitochondria is that there does appear to be a plausible 

 possibility that the mitochondria are actively concerned either in 

 actions themselves enzymatic in nature, or in the manufacture of 



