446 EDWARD E. WILDMAN 
since the identity of each was made certain by its specific pigmen- 
tation. But the localization and pigmentation of these masses 
of eytoplasm—‘organ-forming substances,’ as Driesch calls them 
—is not complete until after the break-down of the nuclear mem- 
brane. Indeed, the material which forms the ‘clear zone,’ from 
which arise the ectoderm and its derivatives, actually comes out 
of the nucleus. All the other masses also are derived as certainly 
from the nucleus, though not so directly, according to Conklin’s 
observations. After describing the formation of the clear zone 
in gasteropod and Ascidian eggs, he says (page 101): 
This truly remarkable condition in which considerable portions of 
the cytoplasm are traceable to the nucleus is of the utmost theoretical 
importance. From all sides the evidence has been accumulating that 
the chromosomes are:-the seat of inheritance material, until now this 
theory practically amounts to a demonstration. On the other hand, all 
students of the early history of the egg have observed that the earliest 
visible differentiations occur in the cytoplasm, and that the position, 
size and quality of the cleavage cells and of various organ bases are con- 
trolled by the cytoplasm. However, in the escape of large quantities 
of nuclear material into the cell body and the formation there of specific 
protoplasmic substances we have a possible mechanism for the nuclear 
control of the cytoplasm; and when, as in the case of the ascidians 
and fresh water gasteropods, these substances are definitely localized 
in the egg, and can be traced throughout the development until they 
enter into the formation of particular portions of the embryo, a specific 
mechanism for the nuclear control of development is at hand, and the 
manner of harmonizing the facts of cytoplasmic organization with the 
nuclear inheritance theory is clearly indicated. 
SUMMARY 
1. Cytoplasmic inclusions of whatever kind found throughout 
the course of spermatogenesis of Ascaris megalocephala are re- 
ducible to two materials, both of which are of nuclear origin: 
(a) the karyochondria, which are derived directly from the kary- 
ochromatin, and (b) the plastochondria, which are derived from 
the plastosome, in part, and in part from the karyochondria. 
2. Both of these appear first in the nucleus of the spermatogon- 
ium. The karyochondria form the surface layer of the kary- 
ochromatin, whether this is in the form of chromosomes or not. 
The plastochondria form the plastosome. 
