STUDIES ON GERM CELLS . 415 



a complete synapsis, such as ordinarily occurs in the germ-cell 

 cycle, and a partial synapsis as exhibited by Dytiscus. Re- 

 garding the significance of this differential mitosis, he maintains 

 that this phenomenon is the cause of the differentiation into nurse 

 cells and oocytes, resulting in a complete amount of chromatin 

 in the keimbahn cells and perhaps also an unequal distribution 

 of cytoplasmic substances. As in the cases of Ascaris and 

 Miastor, it might better be regarded as a means of depriving the 

 nurse cells (somatic cells or abortive germ cells?) of part of their 

 chromatin. Moreover, Boveri ('04) has compared the chromatin 

 diminution in Ascaris with Giardina's differential mitoses. 

 Debaisieux ('09) and Giinthert ('10) have confirmed Giardina's 

 results, and the latter studied two other Dytiscidae (Acilius and 

 Colymbetes) which also exhibit differential mitoses similar ex- 

 cept in certain details. Giinthert found that the chromatic 

 ring is composed of fine granules which may split off from the 

 surface of the chromosomes (compare with Ascaris and Miastor) 

 and stain like cytoplasm. He interprets this as 'Zerfallsprodukte' 

 of the chromosomes. Debaisieux, on the other hand, claims 

 that this cast-out nuclear material is nucleolar rather than 

 chromatic in nature. 



It seems highly probable that the ^anello cromatico' of Giar- 

 dina consists of chromatin, and Goldschmidt ('04) and others do 

 not hesitate to class it as an example of a 'Chromidialapparat.' 

 Furthermore it is apparently the result of a chromatin-diminu- 

 tion, as Boveri ('04) maintains, differing from the similar process 

 in Ascaris and Miastor in details, but not in the ultimate result. 

 Finally, the discovery of' this peculiar body in Dytiscus adds 

 one more argument to the hypothesis that the chromatin content 

 of the germ cells differs from that of the somatic cells quanti- 

 tatively, at least in some cases, and perhaps also qualitatively. 



Many are the bodies that have been homologized with the 

 'anello cromatico' of Dytiscus. Buchner ('09, '10) claims that 

 the nucleolar-like structure in the oogonia and young oocytes 

 of Gryllus is homologous to both the accessory chromosomes of 

 spermatogenesis and to this chromatin ring in Dytiscus. This 

 'accessorische Korper' passes intact into one half of the oocytes 



