428 
J. BRONTE G ATEN BY. 
Spermatid nucleus 
Macromitosome, 
taken as 1. 
greatest length. 
Vanessa urticae 
1 
1*5 
Smerinthus populi 
1 
1-8 
Pieris brassicm 
1 
2-3 
Orgyia antiqua 
1 
1*7 
A comparison of PL 24, fig. 22, and PL 24, fig. 24, of 
Pieris and Orgyia shows why the former should have a larger 
macromitosome in proportion to its nucleus than Orgyia • 
this is the difference in number and collective bulk of the 
mitochondrial bodies. Up to a point this ratio comparison 
holds good, and shows that the more numerous the mito- 
chondrial bodies, the larger will be the macromitosome, but 
it should be remembered that there are also variations in the 
comparative sizes of the nuclei of the spermatids of the 
several species, a fact that must be taken into account. 
There is little doubt that the reason why the Pieris ratio is 
so high is partly due to the smallness of the nucleus (vide 
PL 2$, fig. 22, and compare with Pl. 2$, fig. 24, etc.). .On the 
average, the nucleus is half the diameter of the macromitosome 
(taken in its longest measurement, for it is at this stage ovoid, 
PL 23, fig. 16). Moreover, the figures in Pl. 23, fig. 17, and 
PL 24, fig. 23, show that the ratio of the mitochondrial 
matter (chromophile) may differ from that of the inner 
substance (chromophobe), for the spireme in PL 24, fig. 23, is 
very loosely coiled. 
There is a very important point which should be noted at 
this stage, and which is responsible for the mistaken idea 
(Platner) that the macromitosome (nebenkern) is derived 
from the spindle fibres of the spermatocyte division. I 
pointed out, when describing the mitochondria, that as soon as 
the individual mitochondrial grains began to absorb and form 
within them the inner chromophobe substance, their power of 
resisting acetic acid fixatives become diminished. Near the 
end of growth period, when the mitochondrial mass is large, 
the acetic fixed cell looks like PL 24, fig. 18, the renin ins of 
the mitochondria being still evident (M.L.). But it is when 
