626 The American Naturalist. [July, 
cyanophilous quality of the paternal nucleus is by no means a con- 
stant character. It does not appear improbable that, after the sperm- 
nucleus had become transformed into the male pronucleus, indistin- 
guishable from the female pronucleus in its contour, in its size, in the 
arrangement and the number of its chromosomes—the points strongly 
emphasized already by many workers in this field—the quality of the 
“male” and the “female” substance may no longer be more distin- 
guishable in color reactions than they are in other respects; and that 
such differences as exist between them may be simply those that differ- 
entiate one organism from another of the same species. 
We may say then, that the differentiations of the germ cells in the 
two sexes, which are shown not only in their form and size, but also in 
their chemical qualities, indicated by differential staining, are the 
device indicated (to use figurative language) to secure the union of 
two different individuals, with a special view to effect the transit of the 
male cell to the ovum and that with the successful union, or the close 
approximation, of two germ pronuclei, the “sexes” of the pronuclei 
become lost and they become non-sexual. 
Just what determines the sex of the resulting embryo, which starts 
from this non-sexual stage, is quite another question. 
Since, in general, it is the male that deviates most from the original 
or non-sexual form, the formation of the sperm-cell by a process much 
more complicated than that of the ovum may find a parallel among the 
similar facts in the evolution of the so-called “ secondary sexual char- 
acters.” The “primary” sexual structure—the germ-cell—may be 
said to undergo a series of changes parallel to those that take place in 
somatic structures. The significance of the complicated process of 
spermatogenesis when compared with oogenesis lies in the fact that it 
is part of a general law. 
But if the “ primary sexual character,” a structure taking a direct 
part in reproduction, pursues in its development a path similar to that 
of the development of a “ secondary sexual character,” or structure 
taking only an indirect part in reproduction, it follows that the distine- 
tion between “ primary ” and “ secondary ” sexual character is more or 
less a nominal one—S. Warase, Clark University, Worcester, Mass. 
Non-Sexual Reproduction in Sponges.'—Prof. H. V. Wilson 
of Chapel Hill, N. C., makes an interesting contribution to the subject 
of sexual and non-sexual reproduction of animals in a paper upon the 
