DEGEN EKATE (aPYRENE) SPERM-FORM ATtON OF MOTHS. 473 
the body of the lengthening sperm. The chromatin is thus 
removed from what is the head end of the spermatozoon ; 
now, in the normal sperm the head end is formed by the 
aerosome. In the atvpic sperm the centrosome forms the 
head end, and a very remarkable fact is that the acroblasts in 
the Lepidopterous apyrene sperm follow the chromatin down 
in its path along the lengthening spermatozoon. In PI. 26, 
figs. 8, 5, 7, 8, 11, 12, and 13, this is shown. If the centro- 
some needs to be fairly near the body it influences, we would 
be justified in assuming that the central corpuscle does not 
influence the acroblasts, for they lie a considerable distance- 
from this body. Reference to my previous paper will show 
that the acroblasts of moths keep close to the spermatid 
nucleus, and after approaching one side of the latter, fuse. 
The fused or partially united acroblasts secrete a granule 
which lengthens to form the aerosome. These events happen 
synchronously with the special changes in the nucleus which 
leads to the formation of the elongated, apparently solid,, 
sperm nucleus; thus by the time the nucleus is elongated, 
the aerosome is also elongated and pointed. It has already 
been shown that the chromosomes in failing normally to come 
together to form the spermatid nucleus, often tend to form 
several nuclei of small and varying size. The nuclei fail to- 
retain their position at the sperm head and drift downwards. 
The acroblasts almost invariably follow at the same time, and 
also tend to apply themselves upon rhe chromatic matter as 
they do in normal spermatogenesis. We then come to realise 
that though the chromosomes lack that power which normally 
allows them to reunite to form the spermatid nucleus, never- 
theless they still are able to influence the acroblasts. More- 
over, one often discovers a spermatid in which one small 
nucleus, probably formed from one chromosome, can be seen 
shepherding several acroblasts which are stuck on its surface. 
In these cases I do not think that a normal aerosome is found 
in later stages. That this attendance of the acroblasts upon 
the partially regenerated nuclei is not accidental, and caused 
by the fact that any bodies tend to become cast down the- 
