126 NATURAL SCIENCE [August 
development of insects within the egg. But it is surprising to find 
no reference whatever to parthenogenesis; the fact that reproduction 
by virgin females is common in certain insects is now widely known, 
and some discussion of the subject might be expected even in a much 
more elementary work than this. Nor is there any mention (except 
incidentally on the last page of the book) of the fact—most suggestive 
in its bearing on the possible origin of degenerate groups—that some 
insects become sexually mature in the larval stage. It is hard to 
understand what considerations can have led to such omissions as 
these. 
The concluding part of the book deals with metamorphosis, and 
contains a short summary of the external forms assumed by larvae 
and pupae, and of the development of the imago from the earlier 
stages. The structure of the typical larvae in the great orders is by 
no means fully described ; but there is a more detailed description of 
those interesting forms which pass through what is called a “hyper- 
metamorphosis.” The formation of the adult organs in Lepidoptera 
and Hymenoptera from the imaginal discs is described in detail, 
while a special section is devoted to the corresponding phenomena in 
the Diptera which have been studied better than any other order in 
this connection. Prof. Packard considers the campodiform larva to be 
more primitive than the eruciform, and figures a series of beetle grubs 
which show the transition from the one to the other. In a final 
chapter the fascinating question of the origin of metamorphosis 1s 
discussed ; and the author comes to the conclusion that the trans- 
formations which now characterise all the higher insects have been 
acquired since the group obtained the power of flight. 
A very valuable feature of the book is the full bibliography 
appended to each section; by means of this the student will be 
enabled to follow up any subject on which he desires further informa- 
tion. The figures are numerous, and as a whole good. Though the 
execution is, in some cases, rough, comparing unfavourably with the 
beautiful drawings in the Cambridge Natural History, for instance, 
only a few, such as the larva of Hristalis on p. 430, can be considered 
unworthy of the book. Altogether the work supplies a long felt 
want, and all serious students of insects should be grateful to Prof. 
Packard for having given them in a single volume so full a summary 
of what is known about insect structure and life-history. 
Gro. H. CARPENTER. 
EssEX VERTEBRATES 
Tue MAMMALS, REPTILES, AND FisHEes oF Essex: a contribution to the Natural 
History of the County (Essex Field Club Special Memoirs, Vol. III.). By Henry 
Laver, M.R.C.S., &c. 8vo, pp. 1-138, with 8 full-page illustrations. Chelmsford : 
E. Durrant & Co. ; London : Simpkin, Marshall & Co. 
For many years the attention of those fortunate naturalists who live 
in the-country and have opportunity to observe nature at home has 
been largely devoted to birds, as is indeed natural from the readiness 
with which those creatures are seen and studied, and their own extreme 
attractiveness. It thus happens that while nearly every county in 
the British Isles possesses a popular work on its birds, the other 
vertebrates have been very largely neglected. 
