CYTOPLASMIC INCLUSIONS IN THE GERM-CELLS. 44<1 
in progress, and in Text-fig. ,4 there is drawn a. semi-diagram- 
matic scheme to illustrate the various stages in the formation 
of acrosome and the rotation of the nucleus. 
It is a very difficult matter to make certain in sections as 
to whether the acroblasts are equally divided among the 
daughter-cells during the maturation divisions. They are 
approximately divided, it is true, for the size of the acrosomes 
in any given cyst is the sanje. In Smerinthus there are from 
three to five acroblasts in the spermatid, and one can count 
about sixteen to twenty in the spermatocyte; in Pierids the 
number of acroblasts seems to be greater, but, except* for the 
fact that they are slightly more vesiculiform, the two insects 
have pretty similar acroblastic bodies. In Text-fig. 2, at 5 I 
have drawn schematically what I believe to be the longitudinal 
and transverse section of the acroblast at the end of growth 
of the spermatocyte. In Text-fig. 5 the remarkable behaviour 
of the acroblasts of Pieris is shown during metapliase of the 
second maturation division. The two elements, mitochondria 
and acroblasts, act quite differently. The former are passive, 
and evidently not so easily managed in cell-division as are the 
latter, which collect near the aster. In PI. 25, fig. 48, the 
prophase of the first maturation division is shown. This cell 
not only shows that the mitochondria are visibly affected by 
the spindle-fibres in division, for those near the fibres have 
run together (X.X.), but also establishes, as do most of my 
other figures, that the acroblasts have some definite relation- 
ship with the nucleus and aster. The orientation of the 
acroblast with the concave surface towards the nucleus is 
shown as well in PI. 24, fig. 22, PI. 25, figs. 30, 31, 32, 34, 43, 
and 48, and as a rule is rarely departed from. The reason for 
this curious relationship with the nucleus is unknown to me, 
but it is worthy of notice that this orientation is clearly 
marked from the time one can distinguish the acroblasts in 
the cell, and finally culminates in the attachment of these 
bodies upon the spermatid nucleus. The whole series of 
events seems to show that the acroblast is, especially in celb 
division, a more tractable cell element than the mitochondrial 
