CYTOPLASMIC INCLUSIONS OF THE GERM-CELLS. 421 
properly so called forms a cover for this central core, which 
shows no affinity for the stains mentioned on p. 412— It will 
be seen at a later stage that this colourless inner matter forms 
the mechanism whereby the macro-mitosomal spireme is pro- 
duced. In PL 23, fig. 7 the granules at M.D.T. have the 
chromophobe core already clearly formed, while the grains at 
M.D.X. still are in the midst of forming this core. By stage 
PL 23, fig. 8, every mitochondrial granule consists of the 
inner and outer parts. The inner part is consequently of new 
origin, and has, I believe, no counterpart in the female. Up 
to the end of the growth period the mitochondria increase in 
size, but thenceforth I have not found that their size becomes 
greater. 
A Comparison of the Mitochondrial Bodies in the 
Spermatocytes of Smerinthus populi, Pieris 
brassicte, Spilosoma lubricipeda, Orgyia an- 
ti qua, and Pygmra bucephala. 
An examination of PL 24, figs. 19 (lubricipeda), 22 
(brassicae), and 24 (antiqua) 1 show that these granules 
have a fairly characteristic shape in different families. Smer- 
inthus populi, Pieris brassicae, and Spilosoma lubri- 
cipeda have a mitochondrial body about the same size in 
proportion to the cell contents, but both Smerinthus and 
Pieris have a larger number than Spilosoma; the latter, 
again, has a larger number than Orgyia antiqua. Pieris 
brassicae has mitochondrial bodies similar to those of the 
allied Pieris rapae, and as numerous. Cossus ligni- 
perda and Pygaera bucephala both have mitochondria 
very like those of S. populi. In some ways these structures 
in Orgyia are remarkable. Reference to PI. 24, fig. 24 shows 
that the mitochondria of this species are very large, perfectly 
spherical, and of many sizes. In the material which I had 
1 The Orgyia antiqua material was fixed in Meves’ fluid. From 
preparations subsequently made with my own modification of Flemming, 
1 believe that the mitochondria in my figs. 24 and 27 are abnormal- 
This matter is now being examined. 
