358 
CliESSWELL SHEARER. 
without any division, into one of the nuclei. In fig. 33 such 
a division is shown ; here two egg* masses lie side by side, in 
one of which, that on the right, the male and female sub- 
stance has divided equally, while that on the left shows the 
male portion entirely on one side. The examination of the 
foregoing and subsequent sections of the series shows no 
other portion of the male nucleus present. Similarly in 
fig. 31 we get the same condition. Here in one nucleus the 
male substance is entirely on one side. In the larger oogonial 
masses, such as those already discussed in fig. 22 and fig. 35, 
similar divisions take place. I believe this division to be the 
sex-determining one. The nucleus which has received both 
male and female substance gives rise to the large female 
egg*, while that which has received the female substance 
alone gives rise to the male egg, while all the nuclei in which 
the divisions have been equal degenerate throughout the mass 
of cytoplasm. The evidence for this rests on the fact that in 
the later oocyte stages, when the dimorphism of the eggs, 
male and female, is already clearly obvious, we can still 
distinguish the two portions of 'the nucleus, male and female. 
In the case of the female egg there are always two parts of 
the nucleus, while one only is shown by the male egg. The 
nucleus of the female egg is divided into two compartments, 
as in the early oogonial stages, whereas that of the male egg 
is single and contains only one large chromatic body. 
In fig. 32 is shown on one side two almost fully mature 
female eggs (ov. f.) In this section their large centrally 
placed nuclei are not shown, but at the periphery a nucleus in 
each egg is undergoing the process of absorption. They are 
undergoing obvious disintegration, and stain faintly and 
irregularly. In both, the male and female portions of the 
nucleus show. Therefore those egg s in which the sex- 
deterinining division has taken place have the power of 
absorbing the more immature oogonial cells in which the 
divisions of the nucleus, male and female, have been equal, 
or in which sex-determination has not taken place. 
In the section drawn in fig. 32, a male egg (ov. m.) is 
