MUNSON: SPERMATOGENESIS OF PAPILIO. 
83 
As the chromosome segments are thus drawn towards their respec¬ 
tive poles, they seem still united by the intermediate fibers which 
present in general outline the form of the original spindle (pi. 16, fig. 
113). The connecting fibers seem finer than the original spindle 
fibers; and the question naturally arises whether the original fibers 
are not really composite. I have reason to believe that this is the 
case; for by the application of acetic acid either in stronger solution 
of for a longer period of time, the spindle can be made to swell out 
greatly till it is nearly circular (pi. 13, fig. 38). In this case, the num¬ 
ber of spindle fibers seems greatly increased. On several occasions 
spindle fibers have appeared to be split up into two or more strands; 
and in still other cases they vary greatly in thickness as if some had 
been split while others had the strands still united. 
This may account for the fact that the intermediate fibers seem 
finer than the original ones. It may suggest, too, that the separation 
of the chromatin segments is due to a splitting of the spindle fiber. 
Assuming that each spindle fiber arising from the original nucleus is 
really composite from a double folding on itself of a fiber like the letter 
S, the origin of the intermediate fibers as well as the cause of their 
thinness could be explained. If the two ends of the compressed S 
contract, then the two half chromosomes belonging to each arm of 
the S would be separated, leaving only one third of the original fiber 
as the intermediate fiber. 
Telophase .— Some time after the chromosome segments have 
Beached their respective poles, the cytoplasm begins to constrict at 
the equator, the constriction reaching the spindle before the latter 
begins to disappear (pi. 16, fig. 114). In the living cell, I have watched 
this intermediate spindle for hours, and noted the gradual constriction 
of the cytoplasm, being impressed by the persistence of these inter¬ 
mediate spindles and their remarkable clearness in the living state. 
Second Maturation Division. 
Soon after the first division is accomplished, the cell prepares for the 
second division, apparently before a new nucleus has been developed 
out of the chromosomes. Even before the first division is completed, 
and while the intermediate fibers of the first spindle still exist, the 
centrosomes at the poles divide, each forming two small asters which 
