KARYOKINESIS AND ITS RELATION TO FERTILIZATION. 201 
of the threads occurs not infrequently in daughter-nuclei. 
EK. van Beneden had suggested it as very probable, since in 
fact he found the number of threads greater in them than it 
would be after a single longitudinal splitting. Flemming now 
corroborates this statement, but as to its significance Carnoy 
and Flemming differ considerably from one another, as I shall 
shortly show. Itis further important that Carnoy has observed 
a true “ cell-plate,” in Strasburger’s sense, in the formation of 
the so-called directive corpuscles. It follows, therefore, that 
the formation of the directive corpuscles is to be regarded as a 
true cell-division. Boveri comes to the same conclusion. 
The chief results of Carnoy’s observations, which would 
certainly find a larger circle of readers if they were pub- 
lished more briefly, and in a more widely-read journal, lie 
herein, that he enters a protest against the regularity of the 
so-called karyokinetic law laid down by Flemming (58). The 
karyokinetic process presents so many abnormalities that it is 
as yet impossible to lay down any sound general rule. At all 
events, none of the various phases present in karyokinesis 
appear essential; any may be omitted or may be changed. 
Carnoy repeats, in his last publication, ‘ La Cellule,’ t. iii, 
p- 311, the saying, “ Tous les phénoménes caryocynétiques sont 
variables: aucun d’eux ne pardait essentiel.” 
It is difficult to admit this in regard to that most important 
phenomenon of karyokinesis, the longitudinal splitting, and the 
equal distribution of the sister-threads to the two poles, wherein 
the whole reason of karyokinesis appears to lie, for only in this 
way can the equal distribution of the chromatic substance to 
the two daughter-nuclei be considered as perfectly assured. 
This might also be possible by a symmetrical transverse 
division of the stronger threads at the equator, if it resulted in 
equal-sized portions ; but this is difficult to establish by ob- 
servation. Carnoy, in fact, admits this as a form of karyoki- 
nesis, e.g. in Astacus, Forficula, and Scolopendra (‘La 
Cellule,’ 1885, t. i, fase. 11, p. 334). In many cases, according 
to him, the chromatic segments arrange themselves without 
a previous longitudinal splitting in the axis of the spindle 
