SOME PROBLEMS OF REPRODUCTION. 58 
and both are nieces of the first polar body. I append a schema 
to show these relations (Fig. 9). 
(i) (ii) 
N?p 
w—C N'p 
Np 
/ N*p N’p 
vi 
NAN! zak No N—N N’o 
Fic¢. 9.—i. Schema to show usual formation of polar bodies in Metazoa. 
ii. Schema of polar bodies in Ascaris. 
Unmistakably these processes point to a primitive condition, 
when each ovarian ovum divided in two stages to form a brood 
of four oospheres. Unfortunately the phenomena of the 
gametogenic bodies have been made too much a study isolated 
from other similar formations, and false interpretations have 
been put on the peculiarities of their mitoses to suit preconceived 
ideas. Doubtless had the segmentation of the Metazoan egg 
proceeded after the type of Cystoseira (supra, p. 17), in- 
genious hypotheses would have been framed to explain what 
plasmic properties resided in each of the seven nuclei rejected, 
and for what reason each one had to be expelled from the egg 
to leave a pronucleus fit for fertilisation. 
The remarkable uniformity of oogeny (in the restricted 
sense) in the Metazoa as compared with other equivalent 
groups is perhaps attributable to the fact that its processes 
are usually limited to the short time during which the ovum 
is free before fertilisation, and to the fact that it is usually 
free at that time: a uniformity of external conditions has 
preserved uniformity of results. The much greater variability 
of spermatogeny which takes place under much more varied 
conditions supports this view.® 
1 Blochmann has found in some Insects that the second polar body divides, 
but not the first (“ Zahl d. Richtungsk6rper,'&c.,”’ in ‘ Morph, Jahrb.,’ 1889), 
2] have omitted the consideration of “ paracopulation” in the “ winter 
eggs” of Cladocera, as described by Weismann and Ischikawa (in ‘Zool. 
Jahrb.,’ “ Abtheil f. Anat. u. Ontog. d. Thiere,” iv, pp. 155—196). In 
