36 Bulletin of the Brooklyn Entomological Society. Vol. XIV 
which the adults, as such, could not survive; and natural selec- 
tion would thus tend to perpetuate such forms, thereby tending 
to further develop a propensity toward the production of com- 
plete metamorphosis. This tendency for the immature forms to 
differ from the adults was apparently developed among some of 
the primitive forms in the mild climate and favorable environ- 
mental conditions then surrounding them, and enabled the forms 
which developed this tendency to enter less favorable regions in 
which the more conservative members of the primitive groups 
could not establish themselves. These favored forms were en- 
abled to enjoy the advantage of obtaining more food, under con- 
ditions affording better protection, and less competition; but the 
modifications enabling them to enter these new conditions must 
have been developed before they could enter them, so that I 
would not agree with Handlirsch, 1909 (Die fossilen Insekten), 
who claims that cold, etc., has produced metamorphosis; but 
would rather claim that insects in which the tendency toward 
metamorphosis was already well developed, were better equipped 
than their less fortunate fellows, to penetrate the less favorable 
regions of winter-frost, etc., and there establish themselves. 
This view, however, can perhaps be more clearly set forth by 
comparing it with the views proposed by others concerning the 
origin of metamorphosis. 
Kirby and Spence (Introduction to Entomology) propose that 
the voracious larval stages play a part in the economy of nature, 
being of use in getting rid of decaying animal and vegetable mat- 
ter, but, since the voracious feeding proclivity is somewhat in- 
compatible with the work of reproduction which is of great im- 
portance to the species, it is suspended when the reproductive 
period ensues. This view is in line with Perez’s suggestion 
(Bull. Soc. Ent. France, Vol. LX VIII, Année 1899, p. 401) that 
“V’on peut définir la metamorphose une crise de maturité géni- 
tale,’ which leads to the suggestion that hormones (possibly 
those of maturing gonads, etc.) may play an important part in 
the development of the wing buds and other structures of “adol- 
escence,” and that these hormones or similar substances may 
play an important part in influencing the activity of phagocytosis 
histolysis, and other phenomena of metamorphosis, in conjunc- 
