238 W. WALDEYER. 
together, but have not fused, divides transversely into two 
portions of equal length, each of which forms a U-shaped 
loop. Before the transverse division occurs in the chromatin 
thread, some changes in its position and size take place; it 
moves from the surface of the pronucleus, where it was at first, 
nearer to the centre. We have then four such loops (chromo- 
somes), two male and two female. Hach loop then splits 
longitudinally into two sister-threads, each of which is a true 
image of its fellow, down to the smallest details. Previously 
a spindle figure, composed of threads, which meet at opposite 
poles (the “ sphéres attractives ”), has appeared, as in the karyo- 
kinesis of an ordinary cell. Then the outlines of the hitherto 
perfectly distinct pronuclei disappear. The chromatin threads, 
which have now, by longitudinal splitting, reached the numberof 
eight, four male and four female, take up a position atthe equator 
of the spindle figure. At the two poles, refractive pole bodies 
and polar rays are apparent. The two sister-threads, arising 
from one primary thread, now separate from one another 
towards the poles of the spindle figure; so that the one thread 
moves to pole a, the other to pole 4, and in this way two male 
threads and two female threads arrive at pole a, and the same 
at pole 6. From these two groups of threads respectively 
the chromatin substance of a daughter-nucleus arises; the 
division of the egg-cell now takes place so as to cut 
between the two daughter-nuclei, and the first two seg- 
mentation spheres are formed, each of which contains equal 
amounts of male and of female nuclear elements. I will 
not go further into the other statements of E. van Beneden 
with regard to the behaviour of the chromatin loops during 
the reconstruction of the daughter-nuclei, since in a short 
description it is quite impossible, especially without figures, to 
make oneself understood. But it must be borne in mind that 
the four secondary loops of which each daughter-nucleus is 
composed ,—call them a, 4, c, d,—unite so as to form only two 
loops in the resting nucleus, so that two groups ad and cd arise, 
but these two groups remain independent of one another. Now 
the daughter-nucleus divides anew, during the second segmenta- 
