1904] : CURRENT LITERATURE 67 
in which he holds that we cannot compare an embryonic characteristic with 
an aduit ancestral one, but that embryonic characters only can be compared. 
“Their resemblances are explained on the assumption that there has been an 
ancestral adult form having these embryonic stages in its development, and 
these stages have been handed down to the divergent lines of its 
descendants.” 
The wide scope of the work may be indicated best by an enumeration of 
the titles of the different chapters. There is a chapter on the problem of 
adaptation, two on the theory of evolution, three are devoted to a criticism 
of the theories of natural selection and sexual selection, then come succes- 
sively, the inheritance of acquired characters, continuous and discontinuous 
variation and heredity, evolution as the result of external and internal fac- 
tors, the origin of the different kinds of adaptations, tropisms and instincts 
as adaptations, sex as an adaptation, and finally a summary with general 
conclusions. 
The book is a valuable one both for its clear statement of the problems 
under discussion and for its many new ideas. It will undoubtedly be read 
bya wide circle of biologists and others interested in questions of evolution 
and adaptation.—CHARLES ZELENY. 
The cell of the Cyanophyceae. 
IN REGARD to the structure of the cell of the Cyanophyceae, observations, 
interpretations, and theories have long nee ee and Sed contradic- 
tory, some observers describing cleus thers deny 
ing the existence of such structures, while re less aiicence of opinion ae 
been manifested in regard to other cell contents, the membranes, gelatinous 
envelopes, and the heterocysts. Kohl has just published a book? in which he 
first gives a critical discussion of previous literature, paying particular 
attention to the work of Biitschli, Hegler, Palla, Fischer, Zacharias, and Brand. 
He then describes his own work in great detail, with full illustrations on ten 
colored lithograph plates. Tolypothrix, Nostoc, and Anabaena are the prin- 
cipal forms studied and nearly all of the figures are from Tolypothrix lanata 
and Wostoc coeruleum. 
The following topics are treated: central granules, cyanophycin granules, 
dil, chromatophores, glycogen, membrane and partitions, protoplasmic con- 
nections, “ Verschlusskérper,” vacuoles, chromatic substance, heterocysts, 
concave cells, central body ; with some remarks on the relationship between 
the Cyanophyceae and bacteria. There is also a valuable table containing 
the most important tests and staining reactions. Without attempting to 
separate original views from confirmations and contradictions, the author’s 
results, as gathered from the summary and body of the work, are about as 
2Kout, F. G., Ueber die Organization und die Physiologie der Cyanophyceen- 
zelle und die mitotische Teilung ihres Kernes. 8vo. pp. 240. pls. ro. Gustav Fischer, 
Jena, 1903. 2 
