174 THE CHROMOSOMES 
in other nematodes, where many small chromosomes 
are present, such a loss has been observed from all 
of the chromosomes, which nevertheless retain their 
constancy of number in the germ cells. 
It is not without interest to find in these 
Nematodes with many small chromosomes that the 
female and the male have constantly different 
‘numbers of chromosomes (Edwards, Gulick, Schleip) 
—the additional ones corresponding to the extra 
chromosomes of Ascaris. Thus Edwards finds in 
Ascaris lumbricoides: 
43 chromosomes in the male = 19 + 5 (egg) + 19 
(male producing-sperm) 
48 chromosomes in the female = 19+5 (egg) 
19+ 5 (female producing-sperm) 
In Ascaris incurva, Goodrich has shown (Fig. 36 
M) that a sex chromosome complex consisting of 7 
X-chromosomes goes to one pole of the spindle, so 
that the female-producing sperm has 21 chromo- 
somes; and the male-producing only 14: At the 
time of reduction the X-chromosome complex of 
7 elements shows a tendency to unite more or less 
into a compound element (Fig. 36 M). 
'TETRAPLOIDY 
The fact that ‘pairs of species” are known, one 
characterized by having twice the number of chro- 
mosomes of the other, has suggested that new types 
may arise through doubling of the chromosome 
number. The double chromosome types are larger 
