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ANALYSES OF BOOKS. 
Butterflies , their Structure, Changes, and Life-Histories, with 
Special Reference to American Forms. Being an Application 
of the £< Dodtrine of Descent ” to the Study of Butterflies. 
With an Appendix of Practical Instructions. By Samuel 
H. Scudder. New York : Henry Holt and Co. 
This fascinating volume opens with a curious fact. “ A box of 
butterflies hanging on the wall of a fellow-student’s room in 
college first introduced the author to the enjoyments of a natu- 
ralist’s life.” Mr. Scudder begins his task with an account of 
the structure of the eggs of butterflies, and of the internal 
changes which take place during the development of the larva, 
as far as is yet known. On this subject much work is still re- 
quired. The question further suggests itself, To what extent do 
the forms and the tracery of these eggs — many of which are 
here beautifully figured — exhibit relations in closely-allied species 
and characteristic differences in distinct groups ? Are the pecu- 
liarities of the egg in any way adapted to the circumstances in 
which it is placed ? 
Coming to the caterpillar, we find a careful and well-illustrated 
account of its general structure. In figure 21, representing the 
head of the caterpillar of Danais Plexippus, we note an oversight 
in the lettering : a evidently is a side, and b the front view of the 
head. The author points out in caterpillars two foreshadowings 
of the future state of the insect, or, to speak more precisely, two 
structural peculiarities which have no immediate purpose. Thus 
the spiracles are absent from certain of the median segments of 
the body. The only reason we can see for this arrangement is, 
that in the perfect insect spiracles in this region would interfere 
with the support of the wings and the apparatus for their move- 
ment. Even in the disposition of the spines along the back we 
have a pre-indication of the future separation of the thorax and 
abdomen. 
Not all entomologists are aware that the vesicles of the 
seventh segment of the caterpillars of many of the “ blues ” 
secrete a fluid very grateful to ants, which, in consequence, in- 
stead of devouring the caterpillar, carefully defend it from the 
attacks of ichneumons. 
The author calls special attention to a question which, if old, 
is by no means thoroughly settled : Why do butterflies deposit 
their eggs upon the kind of plant suitable for the nourishment of 
the young? He writes — “ Let us take, for instance, the viceroy 
