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). 
