TEMl’KRATrUK AND .ESTrVATIl )N. 
:!os 
rn)b;il)ly all those substances are fornieil on the same basis, as 
b!eniato]:)ori)b_yrin is yielded on decomposition by all of them. 
The 'rE.Mi’EiiATDRE of wavm-blooded animals is maintained at a 
nearly uniform standard under all changes of external temperature 
by combustive proces.ses within the body, but in the mollusca and 
other cold-blooded animals, owing to their sluggish respiration, the 
oxygenation is so feeble that very little heat is generated and the 
bodil}' temperature fluctuates with that of the inhabited medium. 
Repeated observations have establi.shcil that the temperature of 
land snails practically accords with that of the atmosphere if it be 
moist, but in dry weather the heat of the animals may be reduced 
below th.it of the air, prob.ibly by the increased evaporation from the 
body of its natural moisture. 
Although a single Hi'H.v or Lhna.v confined within a limited space 
causes no perceptible thermometric change, yet if .several be enclo.sed 
together the temperature has been noted by different observers to 
ri.se from D'21° to 
'I'he Relecy])oda likewise maintain a temperature similarly in accord 
with that of tbe water they inhabit, varying in the Anodontw, 
according to different observers, from 1 '0° colder to warmer than 
the respired water. 
d'lsTiVATioN {(isfirfi, to })a.ss the summer) is the period of torpidity 
undergoue during the prevalence of dry, hot, summery weather, and 
though, in this country, this state is essentially transient and short, 
yet in warmer regions this tor])or persists for lengthened periods, 
embracing the entire dry .season, the land mollu.sks con.structiug a 
more or less tilmy and delicate epiphragm (see p. 12!)) and burying 
tbem.s(‘lves more or less deejily in the ground or attaching them.selves 
by a viscous .secretion in some -suitable position. Many freshwater 
.'jiecies also bury themselves deeply in tbe .soft mud when the waters 
they inhabit are becoming dried up. 
Hot dry weather is especially fatal to slugs, which therefore burrow 
into tbe earth and enclo.se tbem.selves within a coating of mucus, 
which on drying ]>revents further evaiioration. 'flic tigurative and 
beautifully e.xpressive simile of the fate of the ungodly given in our 
I’rayer Books, “ Consume away like a snail,” aptly illustrates their 
inability to withstand heat or dryness. 
The forms most subject to seasonal torpidity are naturally tho.se 
most remarkable for their tenacity of life, some species being known 
