468 
J. BRONTE GATENBY. 
formation of an apyrene sperm, began after tbe establish- 
ment of the spermatid nucleus. In Pygaera the second 
maturation chromosomes failed to fuse at all in most cases, 
while, on the other hand, a transition between Pygsera and 
Pieris was provided by Smerinthus where several nuclei 
became formed in the spermatid from a number of success- 
fully fused chromosomes. 
The Nucleus in the Degenerate Stages. 
In PI. 26, fig. 4, is drawn a fairly typical second maturation 
division of the degenerate type which will lead on to the 
abnormal sperm. The two cells are almost constricted from 
each other, but the chromosomes ( C.H .) are straggling, as if 
the centrosome and astral rays lacked the energy to finish 
anaphase and telophase. The mitochondria are normally 
constricting*. The acroblasts are not quite normal, but are in 
the usual position in which they are found. The micro- 
mitosomata are normal. Now this figure is typical of many 
maturation divisions; it shows what most other degenerate 
stages do — that the disintegratory process seems traceable at 
first to the chromatin. It is almost, if not quite invariably 
the nucleus which, in the abnormal growing spermatocyte, 
shows signs of degeneration, and it is the nucleus in other 
stages (PI. 26, figs. 6, 8, 10, etc.) which is the first cell 
element to fail. Inspection of PI. 26, fig. 4, might lead one to 
believe that the centrosome is at fault, but this seems nega- 
tived when one remembers that in later stages the centrosome 
still has the energy to keep its position at the head of the 
cell, to undergo some normal changes, to form the axial 
filament as usual, and finally to enter into its normal relations 
with the mitochondrial spireme. This, at least, points to the 
fact that one must be careful in imputing this abnormal telo- 
phase to the amphiastral rays. In the telophase of normal 
mitosis the chromosomes fuse, and afterwards a new nucleus 
is formed. In these abnormal stages this process rarely takes 
place in the usual manner. The chromosomes either do not 
