GAMETOGENESIS OF SACCOCIRRUS 29 



on the giant germ nurse-cells of Testacella (4) I ventured to 

 interpret certain of my results in this manner, and it must be 

 said that the case of the secondary nuclei is very suggestive. 



There are three possible modes of general interpretation — 

 either the nucleolus represents a second chromatin of some 

 kind, but separate from the chromosomes, or it derives its 

 chromatin from the chromosomes, or there is some cell sub- 

 stance other than chromatin which has the attribute of forming 

 bodies similar to the ordinary nuclei, except for the presence 

 in them of true chromatin. Whether the power of production 

 of a nucleus-like body is to be looked upon as a proof of the 

 chromatinic nature of a granule is unknown. 



(d) On the Special Part played by the 

 Nucleus during Oogenesis. 



Kecent studies on the cytoplasmic inclusions of the germ- 

 cells have revealed the fact that all such units possess both 

 Golgi elements and mitochondria, and that these two categories 

 of formed elements take a prominent part in the upbuilding 

 of the egg cytoplasm. No one has claimed a nuclear origin 

 for the Golgi body, and in my work I have found a complete 

 Golgi apparatus in the earliest germ-cells which have been 

 studied — in molluscs, insects, birds, amphibians, and mammals. 

 The case of the mitochondria is different ; several observers 

 have claimed that they have found the mitochondria to 

 originate from the nucleus during early stages of oogenesis or 

 spermatogenesis. I had never seriously believed these accounts, 

 and still doubt most of them ; but in my own studies on the 

 sponge Grantia I was led to identify the ' chromidia ' of Jor- 

 gensen as the representatives of the mitochondria ; now 

 Dendy firstly, and then I, have shown that the ' chromidia ' 

 of Jorgensen are nucleolar in origin. I still have some doubts 

 as to whether true mitochondria do not exist in Grantia, 

 but my efforts to demonstrate other granules which might be 

 mitochondrial have so far not met with success; therefore 

 I can but assume tentatively that in the case of Grantia the 

 mitochondria are of nuclear origin. 



