REVIEWS. 431 
forces acting upon it are different from those which affect the mature form; and thus 
changes are Aisy in the young which have reference to its immediate wants, rather 
than to its fina 
3rd. That iian may therefore be divided Paes two kinds, developmental and 
adaptational. 
4th. The apparent abruptness of the changes which insects undergo arises in great 
— from the hardness of elr skin, which permits no gratual alveration: of form, and 
ee aor ‘oft the miia or chrysalis depends on the rapidity of the changes 
oris 
6th. Alth ng jority tsg gh th vell 
the egg, still a 1 b i ity tl gh hat indefinite number of 
slight ch 
ith. When xternal organs arrive at this final form before the organs of osd 
tion are S these changes are known as me ae cake het ge the secs 
the organs of reproduction are functionally perfect before th 
the creature has the power of budding, Da the oak is known as i e 
generation: 
Insects present every gradation, fi impl th to alternation of g ti 
8th. Thus, bl 
from the si certain animals leave the egg at a very ane oge “or 
dotia and that the inae forces acting on the young are different from those 
which — * the e mat nre re form 
9th. 
phism of the mature form which we find, for instance, in ants and bees; it would therefore 
oe to distinguish it by a different name; and I have ventured to suggest the 
rms Dicidiom and Polyel dism 
I ‘kabl of generations 
the ee is agamic in the one fi This is because impregnation — the 
-erinan — of external and inter: nal organs; and if the phenomenon gribes, al "on 
been ex 
Eya Actes qere cannot take place, 4 — reproduction will only roonlt pa those pe 
VISION OF THE FossiL H or NORTH America. I. Cra- 
_bronide and Nyssoni iain By A. 8. Packard, Jr., M. D. From the 
oceedings of the Entomological Society. Philadelphia, 1866-67. 
This work treats of the classification of a large group of the fosso- 
or digging wasps. It contains descriptions of nearly all the genera 
and species known to inhabit North America. The species, as well as 
the genera of the digging wasps, are difficult to identify ; but with the 
detailed descriptions of the genera here given, and the synoptical 
table of the species, the work of identification has been rendered com- 
paratively easy. The names of species not seen by the author | are 
added 
of which. one new genus and fifty-eight new species are 
The family characters are discussed at length, and there are a few 
cto 
their zodlogical characters, and geograp phical distribution. 
