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CRESSWELL SHEARER 
of no definite structure, as shown in figs. 38 and 39. In the 
first segmentation division of the male egg this body moves 
over without division into one of the blastomeres and then 
breaks up and disappears. It is not present in the female 
(b) In the Female Egg. 
In the first maturation spindle of the female egg (fig. 37) 
twenty chromosomes are clearly shown. Here, again, twenty 
apparently go out and twenty remain in the egg, for certainly, 
as shown in fis\ 37, eighteen or nineteen chromosomes can 
be counted at each end of the spindle, but as the spindle 
approaches the animal pole of the egg, these chromosomes 
apparently undergo a certain amount of fusion, and when the 
polar body itself is extruded, ten double or dumb-bell 
shaped chromosomes pass out as shown in figs. 47 and 40. 
These then break down into a series of blebs, which take up 
a central position in the egg as shown in figs. 52, 56, and 58. 
It is remarkable that in the female egg the number of small 
nuclei into which the chromosomes break down is remarkably 
constant (fig. 60). I have already said that . I have been 
unable to obtain the second polar body in sections. In the 
spindle of the first segmentation division of the female egg 
twenty chromosomes are seen again at either pole (fig. 62). 
6. Conclusions and Summary. 
The most singular feature of the foregoing work is the 
peculiar manner of early fertilisation and the subsequent 
division of the sperm in the oogonial cells. This would seem 
to be without parallel, although something* similar possibly 
takes place among the Rotifers, where we know from the 
work of Whitney (20) that the eggs undergo part of their 
growth in the presence of the sperm. I have pointed out in 
my paper on Histriobdella (16) that here also the sperm 
nucleus is often found in eggs that are far from fully formed 
and are only about half the size they will subsequently attain 
