262 W. WALDEYER. 
Kultschitzky’s definitions. Undoubtedly van Beneden’s pro- 
position—“ Fertilization is effected at the moment of the com- 
pletion of the two pronuclei”—gives the basis of Kultschitzky’s 
conception of the act; only here the latter stops, whereas van 
Beneden goes further. 
The considerations which determine Kultschitzky to stop at 
this point, and not to admit a further element in the theory as 
to the mode of fertilization, are briefly as follows: —Kultschitzky 
succeeds in showing that both pronuclei in Ascaris regularly 
forma nucleolus, by which would be proved that the pronuclei 
are morphologically fully developed resting nuclei; and one 
ought not to so understand the name “ pronuclei” that some- 
thing is wanting in them for the constitution of nuclei; for a 
greater or less amount of chromatin or achromatin does not 
matter. Moreover, we know that the nucleus is the principal 
element in the life of the cell, and that it is, if not perhaps 
the only, yet the chief vehicle of heritable properties. If, 
then, the male nucleus is introduced into the egg-cell and. 
becomes an integral part of it, then the male influence is 
assured to the egg-cell and to its offspring, the embryo; herein, 
that is, in the restoring and insuring of this influence, lies the 
essence of fertilization. According to Kultschitzky, then, a 
fusion is not necessary, and the “ replacement” of which van 
Beneden speaks may indeed be present, but can be dispensed 
with, in the definition of fertilization. 
In reference to van Beneden’s “ replacement theory,” it will 
here be proper to point out that he and A. Neyt, in their recent 
work (24), call special attention to the fact that in the rest of the 
body-cells of Ascaris megalocephala at each cell-division 
four primary chromatic elements (chromosomes or loops) 
appear, which, before metakinesis, increase by longitudinal 
splitting into eight (secondary loops) ; so that to each daughter- 
nucleus four loops will be given, which have the value of 
four primary loops (chromosomes). As we have already 
seen, the female pronucleus of Ascaris contains only two 
chromatic loops, which, in view of the later processes of divi- 
sion, have the value of primary chromatic elements (chromo- 
