158 
inactive state, their normal constitution would 
be soon affected by their proneness to de- 
. composition, and their peculiar properties be 
bn nd lost. Amongst cold-blooded ani- 
mals, however, we find instances of more com- 
plete suspension of vital actions, which may 
even be prolonged for a considerable period. 
Thus, Spallanzani kept frogs, salamanders, and 
snakes, in a torpid state, in an ice-house, where 
they remained three years and a half, and rea- 
dily revived when again exposed to the influ- 
ence of a warm atmosphere. Insects, in their 
pupa state, may be regarded as analogous to 
plants reduced to bulbs. Although the dura- 
tion of this torpid condition is ordinarily deter- 
minate for each species, and although some 
changes occur during its continuance which 
scarcely warrant us in characterising the state 
as one of entire inactivity, there are some in- 
stances which prove that it may be prolonged 
for an almost indefinite period, under particular 
circumstances. The degree of temperature to 
which pupe are exposed seems to have the 
same kind of influence over them as on the 
eggs of insects. Thus Reaumur found that 
pupe, which would not naturally have been 
disclosed until May, might be caused to un- 
dergo their metamorphosis in a fortnight during 
the depth of winter, by the influence of artifi- 
cial heat; and, on the other hand, that their 
change might be delayed a whole year beyond 
its usual time, by the prolonged influence of a 
cold atmosphere. We can scarcely imagine, 
however, that temperature is the so/e agent in 
accelerating or retarding the final metamor- 
phosis. If the caterpillar of Papilio Macha- 
on, one of those which has annually a double 
brood, becomes a pupa in July, the butterfly 
will appear in thirteen days; if not until Sep- 
tember, it will not make its appearance until 
the June following, that is, not in less than 
nine or ten months. Here it is evident that the 
torpor has been prolonged from some cause in- 
herent in the system itself, for the purpose of 
preventing the disclosure of the butterfly at too 
early a period of the season. A still more cu- 
rious proof of this tendency to prolonged tor- 
idity during the pupa state is the following. 
Tt a number of the pupez of the Eriogaster 
lanestris, a moth whose lJarve are common on 
the blackthorn in June, be selected at the 
same time, and placed in the same circum- 
stances, the greater number of them will dis- 
cluse the perfect insect in the February follow- 
ing; some not until the February of the year 
ensuing ; and the remainder not before the same 
month in the third year. The same has been 
observed of the <Arclea mendica, of which 
thirty-six pupa, grown from eggs laid by the 
same parent, produced twelve perfect insects in 
each of the three following seasons.* The final 
cause of this curious tendency may be, as sur- 
mised by Mr. Kirby, to secure the race from 
being cut off by unfavourable seasons, or by 
some extraordinary increase of its natural ene- 
mies. But its efficient cause can only be looked 
for in some modification of the properties of 
* Kirby and Spence’s Entomology, vol, iii. p. 266. 
LIFE. 
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the organism analogous to that wl 
he phenomena of hylan inc her ani 
e same periodicity, manifesting itself, n 
dallas eo diminished temperatu 
the season of greatest heat, is obse i 
pical climates. Many tribes of insects i 
torrid zone seem to retire to places of re 
during the parching droughts of summe 
make their appearance again during the 
season, when vegetation is in the highes' 
riance. We here trace the e 
adaptation of the phases of animal an 
table life as in the former instances; 
efficient cause which induces these ¢€ 
must be different. 
Our limits do not allow us to dilat 
one very interesting department of this § 
—the prolongation of dormant vitality 
particular circumstances in frogs and 
reptiles. Many marvellous stories of thi 
are on record ;—such as the inclosure 0 
animals in solid blocks of granite or 
igneous rocks, which no well-informe 1 
can credit. There are, however, a sufi 
number of authentic cases to prove, in th 
mation of those who have fairly exan 
them, that toads and other reptiles may] 
closed in masses of rock apparently so 
in the substance of the trunks e 
that they may preserve their vitality unde 
circumstances for a very long period. J 
former instances, it would appear hat th 
mal has fallen into a chink or crevice, 
has been gradually filled up by the wash 
of gravel or other materials disposed t¢ 
dify ; and that thus the a ce of | 
mass has been given, when in reality son 
munication has existed between the cavil 
the external air. It is by no means impos 
moreover, that these animals might be 
imbedded in the sandstones at prese 
course of formation in many localiti 
rocks possessing considerable hardn 
being at the same time sufficiently fp 
allow of the slow passage of air th roug 
substance. Where toads have becom 
bedded in crevices of trees, and bee 
rounded by new layers of wood, it is¢ 
that a direct communication with the a 
phere will probably exist by means 
ginal crevice, although it may be mue 
rowed ; but even if this be not the eas 
porosity of the wood will furnish the re 
condition. Some amount of access — 
would seem, from the experiments of 4 
wards and Dr. Buckland, to be essential 
prolonged vitality of toads enclosed in 
masses ; and this will probably maintain ¢ 
feeble respiratory action upon the blood th 
the general surface, just sufficient to p 
the decomposition of the body. Vital | 
cannot, therefore, be regarded as so comy 
extinct under these circumstances as 1 
of the cases formerly mentioned, where 1 
plication of cold has not only comp! 
checked it, but has also done away wi 
necessity for it, by completely subduit 
tendency to decomposition. ia 
In the human economy, as in that of 
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