606 
J. BRONTE GATENBY. 
some applied to the nucleus. These micromitochondria are- 
about one-fourth the size of the other, or macromitochondria. 
No perceptible variation in size of the micromitochondria of 
various generations has been found. 
(6) The micromitochondria form the front sheath of the 
sperm ; the hind region of the micromitochondrial sheath 
intercommunicates with the macromitochondrial sheath, which 
follows behind. 
(7) The Nebenkern does not apparently become absorbed 
into the substance of the mitochondrial sheath. A sloughing 
off appears to take place. 
(8) The minute cytology of the derivation of the sperms, 
eggs, and nurse-cells is described. 
(9) The determination of the sex of the indifferent cell 
seems to be brought about by a variety of causes. The 
explanation of femaleness by presence of yolk cells is held to- 
be inadequate, for male progerminative cells also appear in 
regions choked with yolk. 
(10) The probable function of the Nebenkern is discussed. 
Addendum A. 
With regard to the body in the spermatids (PI. 32, fig. 24 a,. 
and PI. 33, fig. 35) marked P.N.A. it has lately been found 
that this structure is derived from a number of grains, which 
in the case of Arion I have traced back to the young sperma- 
tocyte. In Helix aspersa these granules could not be found 
in the spermatocyte. P.N.A. stands for post-nuclear apparatus, 
from the position of this structure. The latter is fully con- 
sidered in a forthcoming paper. 
Addendum B. 
With regard to the cytoplasmic bodies in the egg, some 
late papers by Schaxel ( f Zool. Jahrb./ Bd. xxxiv, etc.) are of 
interest. Schaxel claims that the nucleus emits chromatin 
nto the cytoplasm at a brief period after the prophases of 
the heterotypic division. He gives several stages (primary 
chromasie, chromasie post emission, etc.) during which the 
