826 THE AMERICAN NATURALIST. [Vow. XXXIII. 
excess of some of the salts common in sea water. Moreover, eggs 
that have not been fertilized may cleave in such changed sea water, 
and in this cleavage there are divisions and distributions of chromo- 
somes with accompanying activities of centrosomes and of asters. 
There is, of course, room for doubt and for difference of opinion 
as to the light shed by these abnormal processes upon the normal 
ones in the basic phenomena of fertilization and of cleavage. The 
author cites facts that show the power of the egg to cleave without 
the centrosome and the aster, and thinks the chromosome part of the 
nucleus the most influential part of each cell. As cleavage may 
take place without reference to asters, mechanical hypotheses of 
contractile bands or pushing rods seem to him unnecessary. 
Centrosomes, he thinks, may be formed de novo from protoplasm 
outside the nucleus or within it, and may sometimes persist and in 
other cases be of short life. His results are to some extent icono- 
clastic, and he would depose the centrosome from its assumed rôle 
of hereditary monarch. 
The author sees in these results of adding salts no direct mechani- 
cal phenomena, but only the reactions of living eggs when stimulated 
by changed environment. The egg becomes more a living thing 
than it seemed when we were ignorant of these possibilities. 
Holding this standpoint, the author would do well to abandon his 
term “artificial stars,” since it does not appear that these reactions 
to salts are more artificial than those produced by adding sperm, nor, 
in fact, than the reaction of a frog’s leg when salt is placed upon it. 
EB. As A 
History of the Natural Sciences. — The first volume of Danne- 
mann’s Grundriss einer Geschichte der Naturwissenschaften, which 
contains so admirable a series of selections from the works of the 
most distinguished natural scientists of the past, has been supple- 
mented by a second volume,' in which the historical development 
of the natural sciences is dealt with. The subject-matter of this 
volume is largely astronomical, physical, and chemical; and the 
arrangement essentially chronological. While it is to be admitted 
that chemistry and physics are in a sense more fundamental than the 
biological sciences, -and, therefore, deserve a certain degree of pre- 
cedence in an historical account, it is to be regretted that so important 
1 Dannemann, F. Grundriss einer Geschichte eee ac 2. Bd., 
Leipzig, 
Die identity der Naturwissenschaften, 435 pp, 76 illustrati 
W. Engelmann. 1898. 
