504 
L. DONCASTER. 
Stem-mother 4 -f 2 X 
Egg 4 + 2 X 
Egg 4 + 2 X 
Polar body 
4 + 2X 
Polar body 
4 + 2X 
Female -producer 4 -f 2 X Male-producer 4 + 2 X 
Small egg 4 + 2 X 
Large egg 4 + 2 X 
Polar body 
4 + 2X 
Sexual female 4 + 2 X 
Polar body 
4 + X -f X 
Male 4 + X 
Egg 2 (2 + X) Primary sx^ermatocyte 2 x 2 + X 
1st polar body 
2 + X 
2nd polar body Mature egg Functional Degenerate 
2 -f- X sx^ermatid sx^ermatid 2 
2 + X X 2 + X 
Stem-mother 4 -f 2 X 
X shall be extruded or not. So much emphasis has been laid 
on these facts by the opponents of the sex-chromosome hypo- 
thesis that a simple analogy may perhaps be forgiven. If in 
searching for the cause of a disease a pathologist found a 
bacterium, inoculation with which always produced the disease, 
he would be justified in assuming provisionally that this bac- 
terium was its cause. It would be no argument against 
his hypothesis to say that the cause was the injection- 
syringe, or the experimenter, both of which, however, may 
have to act before the cause can take effect. 
In all the examples mentioned hitherto, the female has bad 
