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J. T. CUNNINGHAM. 
elegans, and he was unable to prove that it gave rise to a polar 
globule, but he believed that the spindle and the extruded 
globule were identical, and that the spindle arose from the 
germinal spot. Biitschli's observations initiated a series of 
researches which threw a great deal of light on the history of 
the germinal vesicle. The most complete and trustworthy 
investigations were those of Fol and O. Hertwig ; they 
declared that the polar globules were formed by a process 
identical with that of cell division and were equivalent to cells. 
Balfour, who never formed hasty conclusions, fully accepted 
this doctrine. Another result obtained by O. Hertwig was 
that the two pronuclei in the ovum, the male and female, united 
to form a single nucleus, before the commencement of the 
first segmentation. 
The elaborate investigations of Van Beneden into the history 
of the ovum in Ascaris megalocephala have led to results 
which are in direct contradiction to the prevalent conception. 
He has satisfied himself (1) that the processes which accom- 
pany the formation of polar globules are fundamentally 
different from the processes of normal karyokinesis, that there- 
fore the formation of polar globules is not a case of cell 
division; (2) that the two pronuclei do not unite together to form 
a single resting nucleus : what really takes place is that each 
pronucleus behaves as a nucleus about to divide, and that the 
chromatic V shaped loops and achromatic fibrils formed in each 
contribute to form a single karyokinetic figure. In these two 
points then Van Beneden is in opposition to those authors who 
have hitherto been regarded as most authoritative. He has 
made a complete study of the subject with what seems to be 
eminently favorable material, and gives a detailed account of 
several steps which have before been left in some obscurity. 
It is therefore important as well as extremely interesting to 
examine his figures and descriptions and to enquire, firstly, if 
his conclusions are well founded, and, secondly, what relation 
his results bear to our knowledge of the life-history of the cell 
and of reproduction. 
Material. — Ascaris megalocephala is a Nematode of 
