GERM CELLS IN NEMATODES, SAGITTA 177 
no doubt that a similar process occurs here. The 
general conclusion is reached that the cleavage cells 
of all Ascarip& undergo a chromatin diminution. 
Bonnevie (1901), however, while able to confirm 
Meyer’s results so far as A. lumbricoides is concerned, 
could discover no process of diminution in Strongylus 
paradoxus and Rhabdonema nigrovenosa. 
The elimination of chromatin from all of the 
somatic cells of Ascaris and not from the germ cells 
led to the conclusion that the germ-plasm must re- 
side in the chromatin of the nucleus. The more 
recent experimental investigations of Boveri (1910a, 
1910), however, indicate that it is not the chromatin 
alone that determines the initiation of the diminu- 
tion process, but that the cytoplasm plays a very im- 
portant role. Dispermic eggs were found to segment 
so as to produce three types as follows: 
Type I, with one stem cell (P) and three primordial 
somatic cells (AB) ; 
Type II, with two stem cells and two primordial 
somatic cells; and 
Type III with three stem cells and one primordial 
somatic cell. 
Fig. 53, B shows a cleavage stage of Type II. 
Here are represented two stem cells (P) with the com- 
plete amount of chromatin, both of which are pre- 
paring to divide to form the stem cells (P:) of the next 
generation. From the study of these dispermic 
eggs Boveri (1910) concludes! that it is “die unrich- 
1“Durch die simultane Vierteilung eines dispermen Ascaris-Eies 
entstehen (vielleicht mit ganz seltenen Ansnahmen) Zellen, welche die 
N 
