Recent Advances in the Study of Heredity. 3 
of the two sets of sperms, which have the following chromosome 
formula :— 
(a) \ (c + x) £ c 
or (b) \ (c + x) | (c + y) 
where c — the number of chromosomes common to both kinds of 
sperms, y = 1 peculiar chromosome, x = 1 to 4 peculiar 
chromosomes. It may be noted here that the x- and y-elements 
are “ synaptic mates,” as indicated in the spindle in Fig. 4. 
A remarkable fact has now to be related. In species pre¬ 
senting dimorphic sperms as just described, it is found that the 
//I\ (' 
0 H 0 
toil) ftA 
</ujyvj ay 
h @)+(ow) = \(my 
V ©*(w) ■ (Jf 
, * 
j S ai 
A $ 2.X 
K <in f 
0®0 
*-A\// 
• <a> + (<’3> - (Lj) 
JJ) (noo) + 
' \w00)/ 
) S sr 
? 98 
Fig. 4. 
Fig. 4. Diagram of cytological phenomena manifested in gametogenesis 
and in the soma of certain insects (after Wilson 1 ). 
x = x-element or accessory chromosome, 
y = y-element, a = male-producing sperm, 
b = female-producing sperm. 
* These numbers refer to Anasa only. 
somatic cells of the male and female are different in their chromo¬ 
some characters! The female somatic cells have (2 c + 2 x) 
chromosomes, where c = equals the number of chromosomes 
common to the two kinds of sperms, and x = the x-element again ; 
but the male somatic cells contain either (2 c -f 1 x) or (2 c + x 
+ y) chromosomes according to whether half the sperms have a 
y-element or not. Now it has been found that the ova eliminate 
1 Recent Researches on the Determination and Heredity of Sex. 
Science, N.S., Vol. 29, No. 732, pp. 53-70. 
