1864.] Canpnntrer on Correlation of Physical and Vital Forces. 261 
assimilated during their larva state.* But those whose period of 
activity is prolonged, and upon whose energy there are extraordinary 
demands, are scarcely less voracious in their imago than in their larva- 
condition ; the food they consume not being applied to the increase of 
their bodies, which grow very little after the assumption of the imago- 
state, but chiefly to their maintenance ; no inconsiderable portion of it, 
however, being appropriated in the female to the production of ova, 
the entire mass of which deposited by a single individual is sometimes 
enormous. That the performance of the generative act involves not 
merely a consumption of material, but a special expenditure of force, 
appears from a fact to be presently stated, corresponding to that 
already noticed in regard to Plants. 
Now if we look for the source of the various forms of Vital force, 
—which may be distinguished as constructive, sensori-motor, and 
generative,—that are manifested in the different stages of the life of an 
Insect, we find them to lie, on the one hand, in the Heat with which 
the organism is’supplied from external sources, and, on the other, in 
the Food provided for it. The agency of Heat, as the moving power 
of the constructive operations, is even mere distinctly shown in the 
development of the larva within the egg, and in the development of 
the imago within its pupa-case, than it is in the germinating seed ; 
the rate of each of these processes being strictly regulated by the 
temperature to which the organism is subjected. Thus ova which are 
ordinarily not hatched until the leaves suitable for the food of their 
larvee have been put forth, may be made, by artificial heat, to produce 
a brood in the winter; whilst on the other hand, if they be kept at a 
low temperature, their hatching may be retarded almost indefinitely 
without the destruction of their vitality. The same is true of the pupa- 
state ; and it is remarkable that during the latter part of that state, in 
which the developmental process goes on with extraordinary rapidity, 
there is in certain Insects a special provision for an elevation of the 
temperature of the embryo by a process resembling incubation. 
Whether, in addition to the heat imparted from without, there is any 
addition of force developed within (as in the germinating seed) by the 
return of a part of the organic constituents of the food to the condition 
of binary compounds, cannot at present be stated with confidence: the 
probability is, however, that such a retrograde metamorphosis does 
take place, adequate evidence of its occurrence during the incubation 
of the Bird’s egg being afforded by the liberation of carbonic acid, 
which is there found to be an essential condition of the developmental 
process.—During the larva-state there is very little power of main- 
taining an independent temperature, so that the sustenance of Vital 
Activity is still mainly due to the heat supplied from without. But 
in the active state of the perfect Insect there is a production of heat 
* Tt is not a little curious that in the tribe of Rotifera, or Wheel-animalcules, 
all the males yet discovered are entirely destitute of digestive apparatus, and 
are thus incapable of taking any food whatever; so that not only the whole of 
their development within the egg, but the whole of their active life after their 
emersion from it, is carried on at the expense of the store of yolk provided by the 
parent. 
VOL. I. dh 
