140 GERM-CELL CYCLE IN ANIMALS 



into the cytoplasm in all except the "stem-cell" 

 during the early cleavage of Ascaris is well known 

 (see p. 174, Fig. 51). A similar process was described 

 by Kahle (1908) in Miastor metraloas and confirmed 

 by me (Hegner, 1912, 1914a) in Miastor americana 

 (see p. 57, Fig. 16). This chromatin-diminution 

 process results in the formation of a single primordial 

 germ cell containing the complete amount of chroma- 

 tin and a number of somatic cells with a reduced 

 amount of chromatin. The origin of the germ cells 

 has been carefully studied in a number of forms which 

 in other respects resemble Ascaris and Miastor, but 

 in none of them has such a process been discovered. 

 Hasper (1911) was unable to establish it for Chirono- 

 mus which is very similar to Miastor in early develop- 

 ment, nor has such a phenomenon been found in Sagitta 

 (Elpatiewsky, 1909, 1910 ; Stevens, 1910&; Buchner, 

 1910a, 19106) and the copepods (Haecker, 1897; 

 Amma, 1911) and Cladocera (Kuhn, 1911, 1913) 

 which undergo total cleavage and are in certain 

 other respects similar to Ascaris. 



The nuclear divisions in the eggs of chrysomelid 

 beetles have been examined by the writer with con- 

 siderable care, but nothing resembling a diminution 

 process was found. Furthermore, there are no 

 evidences of chromatin bodies in the cytoplasm or 

 yolk as in Ascaris (Fig. 51) and Miastor (Fig. 18, cR), 

 where the cast-out chromatin does not disintegrate 

 immediately, but can be distinguished for a consider- 

 able period during early embryonic development. 

 It seems necessary to conclude therefore that in 



