Q12 GERM-CELL CYCLE IN ANIMALS 
parts of the cytoplasm by some investigators; in 
some species they are extra-cellular bodies, such as 
nurse cells. 
The accompanying table indicates the number and 
diversity of the animals in which keimbahn-determi- 
nants have been described, and shows the increasing 
interest that has been given to this subject within re- 
cent years, over half of the papers listed having been 
published since 1908. Several cases have been re- 
ferred to in the text, but omitted from the table be- 
cause of insufficient evidence regarding their connec- 
tion with the primordial germ cells. The list as 
given includes representatives of the C@LENTERATA, 
CuzatocnatHa, Nematopa, ARTHROPODA, and VER- 
TEBRATA. The terms applied to the various sub- 
stances have been chosen evidently because of their 
genesis, position in the egg, or supposed function. 
TaBLeE oF PrincipaL Cases OF VISIBLE SUBSTANCES CON- 
CERNED IN DIFFERENTIATION OF GERM CELLS (IN CHRON- 
OLOGICAL ORDER) 
NAME oF SPECIEs, Name APPLIED TO 
Genvs, or Group SUBSTANCE AUTHORITY Date 
Chironomus nigro- | Dotterkérnchen | Weismann 1863 
viridis 
Miastor Dottermasse Metchnikoff 1866 
Moina rectirostris | Richtungskérper | Grobben 1879 
Chironomus Keimwulst Ritter 1890 
Daphnidee Paracopulations- | Weismann and | 1889 
zelle Ischikawa 
AL quorea Metanucleolus Haecker 1892 
Ascaris megaloce- | Chromatin Boveri 1892 
phala 
