236 W. WALDEYER. 
The protoplasm of the spermatozoon, together with the 
refractive body (the fate of the membrane has already been 
indicated), separate from the chromatopbilous body and the 
halo, and mix with the egg-protoplasm ; occasionally van 
Beneden also found remains of the refractive body in the so- 
called “ perivitelline fluid,” which separates from the egg during 
this process (see Pl. XIV, fig. 14). The protoplasm does not sepa- 
rate until later, and for a long time the male pronucleus during 
its completion is still surrounded by it like a cap. What now 
becomes of the separated part of the spermatozoon, whether it 
is to be regarded simply as an outcast which will be assimilated 
by the egg (EH. van Beneden uses the word “ digestion”), or 
whether its mixture with the egg-protoplasm is also an act 
necessary for fertilization, is at present undecided. I shall 
return to this point again. 
The remainder of the spermatozoon—the chromatin body 
and the clear area round it, which HE. van Beneden regards as 
nuclear substance,— becomes transformed into the male pronu- 
cleus. The chromatin body often appears to be composed of 
two distinct portions. The mode of transformation has been 
minutely described by van Beneden. Essentially the chro- 
matin body is seen to be changed into a fine network in which 
a single loop appears later on. This thread consists of an 
achromatic ground substance with chromatic granules as vari- 
cosities on it; an envelope of small achromatic granules is 
also formed round the whole. From the main thread, however, 
finer threads are given off, in various places, which form a fine 
network underneath the envelope. All this is filled in with 
the clear substance. Since the mass of the pronucleus increases 
continually, we must admit that it assimilates part of the sur- 
rounding egg-protoplasm. 
Just in same way as the male pronucleus is formed from 
part of the nucleus of the spermatozoon, so is the female pro- 
nucleus formed of the nuclear remnant of the egg, after the 
separation of the directive corpuscles. This nuclear remnant 
now contains only a quarter of the original chromatin sub- 
stance of the germinal vesicle. But here, too, it seems, as in the 
