MATURATION AND FECUNDATION OF THE OVUM. 129 
ovum throws off certain parts of its nucleus. It is very 
plausible to suppose that the part of the nucleus thus eliminated 
is the male part, and the ovum after the expulsion of polar 
globules thus differs essentially from an ordinary cell. Van 
Beneden therefore calls the ovum containing a female pro- 
nucleus a gonocyte. 
In the development of spermatozoa also, some part is thrown 
off — the cytophore or blastophore, described in very many dif- 
ferent animals. In Ascaris megalocephala a spermatogo- 
nium divides into two cells — the spermatogemmse ; each of 
which divides into four cells — the spermatocytes, which be- 
come spermatozoa. Between the four spermatocytes is the 
cytophore, composed of four parts, one derived from each 
spermatocyte. Each part of the cytophore contains an ele- 
ment which takes up carmine, but whether it is derived from 
the nucleus of the spermatocyte Van Beneden does not know. 
In a subsequent memoir , 1 of which I have only been able to 
see an abstract, Van Beneden and Julin have discovered a 
globule thrown off by the spermatogonium of Ascaris mega- 
locephala before the cytophor is formed. They believe this 
globule to be expelled from the nucleus in the same way as 
described by Van Beneden in the ovum, and to be equivalent 
to a polar globule ; the cytophore is not formed by a process 
equivalent to cell division. Yan Beneden then concludes that 
the spermatozoon has lost the female part of its nucleus, and 
is a male gonocyte. The two gonocvtes unite to form a 
complete hermaphrodite cell. 
With regard to the opposition between himself and previous 
investigators, Yan Beneden points out that the discrepancies 
cannot be due to his methods or interpretation, because in the 
segmentation of the ovum his results confirm and extend those 
of earlier researches. If he recognised normal karyokinesis 
in the one case he was able to do so in the other if it existed. 
1 ‘ Bull. Acad. Roy. Belg.,’ vii, 1884, p. 312. 
VOL. XXV. NEW SER. 
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