982 THE AMERICAN NATURALIST. (Vor. XXXIV. 
the egg, yet in this case we start with only the nine of the sperm 
and have no egg nucleus at all in the fragment studied. Delage 
concludes that the constant number of chromosomes, 7, is a con- 
stant factor of the cells, as are the contractile or secretive functions 
of cells, and that it is not produced by the activities of chromosomes 
acting as individuals. 
In the last paper he defines his position as to the meaning and 
nature of fertilization. Assuming that experiment has shown that a 
piece of egg protoplasm, with no nucleus, can form an embryo if 
combined with a sperm, and not otherwise, he affirms that the essen- 
tial thing in fertilization is this union of egg cytoplasm with the 
sperm. The egg nucleus is not necessary for the formation of a 
larva. Moreover, his experiments show that the per cent of frag- 
ments developing is larger than the per cent of whole eggs develop- 
ing under given conditions, and he infers that the egg nucleus is not 
only unnecessary, but even a hindrance to fertilization. 
In normal fertilization he regards the nuclear phenomena as rather 
a substitution of a male for a female nucleus than as a combination 
of the two. He does not deny that the egg nucleus is of use to the 
race in aiding in handing down characters of the maternal side, it 
may be; but to the making of the individual it is not useful, but 
detrimental. 
Accepting the recent experiments upon echinoderm eggs, in which 
they are stimulated by chemical agents to develop parthenogenet- 
ically, he supposes that in fertilization the sperm nucleus is the 
active stimulating factor, while the egg nucleus is inert — to such an 
extent as to inhibit the sperm to some extent. Extending this idea, 
he supposes that the process of maturation of the egg is to be inter- 
preted as follows. The polar bodies take from the egg nuclear 
matter and so reduce the inertness of the egg nucleus to a point 
where the sperm may overcome what is left. Were there no polar 
bodies, the sperm could not overcome the inertness of the entire 
egg nucleus. FA 
Skeleton of the Black Bass. — The skeleton of the black bass, 
on which Dr. Shufeldt has already made several interesting reports, 
has been described by him in full in a recent memoir.’ This is 
accompanied by eight well-executed figures which illustrate in par- 
ticular the structure of the skull of this fish. The text includes 
1 Shufeldt, R. W. "The Skeleton of the Black Bass, U. S. Fish Comm. Bul- 
letin for 1899, pp. 311-320. 
