188 GERM-CELL CYCLE IN ANIMALS 



deeply by nuclear dyes which was found by O. Van 

 der Stricht (1909) in the bat at the time of the first 

 cleavage mitosis may be similar to the "corps enig- 

 matique" of the cat. 



In many animals no keimbahn-determinants nor 

 similar bodies have as yet been discovered. The best 

 we can do in cases of this sort is to determine from 

 what cleavage cell or cells the germinal epithelium 

 probably originates. For example, in Arenicola, 

 Lillie (1905) has shown that the part of the perito- 

 neum from which the germ cells arise develops from 

 teloblast cells which are probably derived (Child, 

 1900) from cell 4d. At present, however, no charac- 

 teristics have been discovered which enable us to 

 distinguish between the germ cells and the somatic 

 cells in the early embryonic stages of such animals 

 (Downing, 1911). 



