Reviews, 
269 
sense organs is especially good. The clear descriptions are illustrated 
hy well-drawn figures and a few good photographs. Second-rate half- 
tone blocks such as illustrate (?) anatomical detail in certain recent 
American publications are pleasingly absent from the present volume. 
The chapter on development is good as far as it goes, but both embryolo- 
gical and post-larval growth might have been more fully treated with 
advantage. The recent positive statements of Heymons and Lecaillon 
that the "mid-gut" of winged insects arises from the ectoderm deserve 
at least a passing mention. 
The summary of the various theories of organic evolution given by Dr. 
Folsom is effective and impartial. He appears to be a Darwinian in 
Darwin's sense (not in Weismann's), and his mind is open to the factors of 
isolation and mutation advocated in recent years by Romanes and 
De Vries. It is surprising, however, to miss from this summary any 
mention of Mendel's work. The inclusion of these general topics in an 
entomological text book is fully justified by the light which the study of 
insects can throw on their solution. 
A strong feature of the book is the section devoted to the bionomics of 
insects. The chapters dealing with coloration, plant and insect relations, 
and insect habit, are full of interest, and some results of the recent 
researches of Janet, Moller and the Peckhams, on ants and other 
Hymenoptera are readily available for the English reader. Perhaps the 
author is too ready to accept as explaining details of insect behaviour the 
" tropic " terminology of Loeb and other recent experimenters. Reflexes 
doubtless play a large part in the actions of insects, but the " reduction " 
of memory and consciousness to reflexes is more than " improbable." 
The chapter on distribution contains a valuable summary of recent work 
on fossil insects, with figures of the most remarkable forms. The geo- 
graphical section of this chapter gives the first indication that the book is 
primarily meant for American students, on account of the predominant 
attention paid to the problems presented by the distribution of insects in 
the United vStates. Many of these problems, however, have an interest for 
the Kuropean zoologist, who may be grateful to Dr. Folsom for bringing 
together in a convenient summary many facts scattered in the enormous 
economic literature of American entomology. In the discussion of the 
world-regions no mention is made of the proposal — first put forward 
by Merriam and subsequently advocated by Scharff"— to establish the 
Sonoran as the headquarters of a fauna distinct from the Holarctic. And 
by some curious slip it is stated that the Kuploeinae— a group of butter- 
flies most characteristic of the fauna of the Kastern tropics— "are 
restricted, almost without exception," to South America. 
But for the book, on the whole, we have nothing but praise, and not 
the least obligation which Dr. Folsom has conferred on the student is 
the admirable bibliography occupying 57 pages and containing over 1,000 
references. 
G. H. C. 
