KARYOKINESIS AND ITS RELATION TO FERTILIZATION. 185 
the formation of animal cells, so that we do not expect knob- 
slike thickenings of the spindle-thread such as are found in 
plant-cells. However, Mayzel describes a similar appearance 
in the division of endothelial cells of the anterior chamber of 
the eye, and E. van Beneden in the division of the Dicye- 
mide a low group of animals. Flemming, too (50), records 
on p. 246 that, in the commencing constriction of the cells, 
threads in many cases stretch: distinctly to the equator; he 
was, however, unable to determine whether these threads were 
connected with the original spindle figure. On this point 
ef. Carnoy (47) in his discussion on the directive corpuscles, 
p. 46. 
In Rabl’s memoir (165) we read on p. 282 that at the pole 
of the daughter-star a clear, strongly-refracting mass is appa- 
rent, which “ undoubtedly ” arises from the remains of the 
spindle-threads. 
Well worthy of notice are the views of Platner (159) and 
La Valette St. George (121) that, in the formation of Sperma- 
tozoa, during the last of the mitotic divisions which are here 
present, the spindle-threads are converted into the so-called 
“‘ paranucleus.”’ Compare the very careful and minute researches 
of Prenant (168). 
Only a few authors have occupied themselves with the polar 
rays, and yet I think with Fol (68) that these must be regarded 
as of great importance. Auerbach (5), one of the first to study 
the ray-formation, regarded it as an expression of the disin- 
tegration of the nucleus, and as a distribution of the disinte- 
grated nuclear substance to the cell-protoplasm ; he called it 
therefore the “ karyolytic figure.” Strasburger, as we know, 
speaks in favour of the intermixture of cell-sap and nuclear-sap 
during karyokinesis, yet we need not refer the radiating polar 
figure to it. The most detailed accounts of this important 
subject have been given by E. van Beneden and Platner. The 
former, from the commencement of his researches, has given 
the greatest attention to the processes in the cell-protoplasm 
during mitotic division. Thus, he shows that the protoplasm 
of cells whose nucleus is preparing for karyokinetic division 
