CHROMOSOMES AND MITOCHONDRIA 267 
chromosomes, and generation after generation of 
such females appear during the summer; but in 
the autumn, females, whose eggs must be fertilized 
before they will develop, and males are produced. 
The chromosomes of these eggs are distributed during 
maturation as shown in the diagram (Fig. 72). 
The eggs that develop into the females possess the 
usual number of chromosomes, but those that give 
rise to males cast out in the polar body one chromo- 
some that fails to divide, and hence are provided 
with one chromosome less than the others. During 
the maturation of the germ cells of these males two 
sorts of spermatozoa are formed, one with three 
chromosomes, the other with only two; the latter 
degenerate. Therefore, since only one sort of 
spermatozoa is functional, the fertilized winter 
eggs are all alike and all give rise to females (stem- 
mothers) the following spring. 
The chromosome distribution in certain nema- 
todes resembles somewhat that of the phylloxerans. 
Here, however, we have to deal with organisms that 
are peculiar in several respects. Maupas (1900) 
has shown that in the genus Rhabditis the number 
of males per 1000 females ranges from 45.0 to 0.15 
according to the species; and that these few males 
do not copulate with the females and hence are func- 
tionless. Furthermore, the females are not true 
females, but hermaphrodites. Kruger (1912) dis- 
covered that in Rhabditis aberrans the nuclei of the 
spermatozoa did not fuse with that of the egg, except 
in one instance, but disappeared in the cytoplasm ; 
