200 W. WALDEYER. 
Before I pass on to these considerations, some other abnormal 
forms of karyokinesis must be reviewed, and certain pecu- 
liarities brought together, which without a great digression 
could not well have been included within the compass of the 
previous descriptions. The process of cell-division must also 
have due consideration. 
Sanfelice (176) describes a peculiar case of mitosis during 
spermatogenesis. An achromatic spindle is formed, at the two 
poles of which the chromatin is accumulated ; then the latter 
separates from each pole in the form of a spherical body, and 
rests freely in the body of the cell; then division of the spindle 
takes place, and the reunion of each chromatic sphere with one 
half of the spindle follows ; then the division of the cell occurs. 
As to the important question about the cause of the 
movement of the chromatic loops from the equator to the 
poles (metakinesis), it should here be mentioned that E. van 
Beneden (28, 24) compares the thread structure of protoplasm 
with the fibrillar structure of muscular tissue. He considers 
the achromatic threads of the spindle figure as contractile, 
especially as he saw the small granules which compose them 
approach one another and then separate. He is of opinion 
that the threads of the spindle figure stand in connection with 
the pole bodies on the one hand, and with the chromatic 
threads on the other, so that the latter, by the contraction of 
the spindle-threads, will be drawn towards the poles. This 
opinion is also held by Boveri (34). E. van Beneden, especially, 
goes very closely into the structure of the protoplasm and 
nucleus in his often quoted memoir. Platner (161) holds similar 
views. I cite these views with especial reference to a question 
which is again giving rise to discussion, viz. what is the true 
element of the organism—is it the cell or the nucleus, or is it 
the most minute parts which were first named ‘‘ microsomes” 
by Hanstein (86), (Mikrozymas, of Béchamp) and “ granula” 
by Altmann (2) ? 
We find in Carnoy’s works (46—48) no small divergencies 
from the hitherto described mode of karyokinesis. He was 
certainly the first to maintain that the longitudinal splitting 
