KARYOKINESIS AND ITS RELATION TO FERTILIZATION. 241 
kérper,’ |. c., p. 62) is of the same opinion ; he would, however, 
regard the paranucleus as the “ first directive corpuscle.” 
So significant a work as the one referred to and one so 
greatly revolutionising our previous ideas, could not fail to 
provoke new researches as well as contradiction. Much that 
EK. van Beneden has obtained may be regarded as the assured 
property of science. At the same time the very striking 
assertion that in fertilization we have to deal, not with a 
fusion, but with a distribution of chromatic nuclear sub- 
stance, as well as the closely connected consequence of the 
hermaphrodite nature of the cell, and the significance of the 
directive corpuscles, has been actively opposed. We will now 
turn to the accounts which confirm the facts brought forward by 
van Beneden, as insisted upon in his latest work published in 
conjunction with A. Neyt (24). He allows that in a very 
small number of cases a “fusion”? of the two pronuclei does 
occur (p. 28), but maintains with truth that the process is 
meaningless in face of the fact that it can only be observed 
quite as an exception (“ Les deux éléments (pronuclei) repré- 
sentent ensemble un noyau complet et il est absolument 
indifférent qu’ils accolent et se fondent ou non l’un avec 
Vautre puisque, chez lAscaris, cette fusion n’a pas lieu dans 
Vimmense majorité des eufs”). Again, on p. 36, van Beneden 
rightly points out the difficulty which exists in those cases where 
both pronuclei are situated close to one another; here it is 
impossible to determine whether the chromatin of the two 
pronuclei has met and fused or not. It is then, of course, 
inadmissible to assert in such cases that a true fusion has 
taken place. To all such uncertain cases there is always 
opposed the majority in which we can be positive that no 
fusion occurs at any time. 
Boveri (34) is, in regard to the fusion, quite in agreement with 
van Beneden ; so also is Kultschitzky (115, 116), whose prepara- 
tions have been submitted to me, and with whom I fully agree. 
We are unable to establish a fusion in a single Case. 
It seems to me especially valuable that in quite a different 
object—Arion empiricorum—van Beneden’s account can 
