CULTURES OF SPERMATOZOA 385 
After the spermatozoa have been left in contact with the cul- 
ture medium for about eighteen hours no more, or but very few, 
of these uniformly stained vesicles are to be found. But there 
are many fairly normal looking nuclei in which the chromatin is 
all present in the shape of discrete particles resting on the nuclear 
wall, and in which no linin, or but very small amounts of it, can 
be seen (figs. 8 to 11). The principal reason for believing that 
a certain amount of linin is present, even if it is obscured by the 
chromatin, is that some vesicles are seen, which seem to have 
broken away from the spermatozoa before they came in contact 
with the sperm head, and which do not contain any chromatin 
at all. In these a few strands of linin-like substance may usually 
be seen traversing the interior of the vesicle; and it is likely that 
these strands are also present in the other vesicles but cannot be 
made out on account of the chromatin. 
It would seem probable that the chromatin in these nuclei is 
derived by a condensation of the uniformly distributed chromatin 
of the previous stage, though it is possible that in a certain num- 
ber of cases the sperm head breaks up into chromatin Particles 
without a previous complete solution. 
Ordinarily no signs of either protoplasm or sperm tails are to be 
seen in connection with these nuclei but occasionally. both may 
be observed, as in figs. 8b and 10a; and in several cases it was seen 
that the middle piece had not been incorporated within the nucleus ~ 
or vesicle but could be distinctly made out in the tail attached to 
the vesicle. 
When the preparations are fixed in Flemming’s fluid, stained 
with Czaplewsky’s carbolic gentian violet, dehydrated and 
mounted in balsam, clearer pictures of the completed nuclei were 
obtained (figs. 9 to 11) but the series of intermediate stages in 
the formation of these nuclei seemed to be entirely different. It 
was possible to make out a connected series of transformations 
of the sperm head into nuclei, but since this series contained none 
of the vesicles so characteristic for the living and glycerine mate- 
rial it must be concluded that this series is composed mainly of 
artefacts resulting from the shrinkage of the vesicles. 
