AI111111g the invertebrates, land-snails hibernate within their closed shells. They also afford the most. conspieuous .1tnerican example of estiva. tion. \\hen the dry, hot weather of midsitin tiler approaches .come two three the aperture of their shells. and behind these remain as torpid as in winter until tempted out by a prolonged shower, until the autumn coolness 111111 dampness arrive. Slugs bury themselves in the ground, and the bi• valve mollusks in the mud it the bottom of streams 11011(k. .k great many of the other land invertebrates survive as egg: or spore: remain during the winter, and begin to develop on the return of spring. Spi ders, more or less active, hide under fallen leaves ur bark. and in ot her secluded places. Insects pass the in all stages of 11111'11 /p1111`11t. number of beetles. flies. 81111 11 few butter flies winter as adults in northern climates. .\ large of butterflies and moths the winter as pular, freptently protected by a silken eoc4/011. Several kinds of caterpillars are able to stirvive the winter either in spun or in sheltered hollows or chinks. A vast host of insects survive as eggs, whose development delayed until spring.
Upon waking from their stupor the heat of the animals Ver• quickly 111 10 normal. Hunger is probably the
chief agent that calls such animals 10 activity again. The most profound sleepers van scarcely he kept awake when brought into a warm room and stimillated. Partial 'di...rimier-. after a hearty meal in winter, re•itim. their torpor again. The air tinder it bell jar, in which a hibernating dor mouse is put, remains unchanged. Hall kept a hibernating bat under water fifteen minutes with out fatal effect. while a wakened bat will sue. eimili after three ininntes. Carbon dioxide, which is speedily fatal ill :111 VI' has no etieet on a torpid marmot. II ibernaters lose their weight in winter to the extent of :10 to AO per cent. This loss of weight indica IPS that, not withstanding their great diminution, the vital processes are going on in the hibernating animal all the time.
Consillt : hall. "Ilibernation." in Todd. r'yelo pallia .1 tut tom y and l'h ystob)gy. vol. ii. ( Lon don, 1 ti3h) ; Browne. .1 y and i bermaion I Philadelphia. Is; ; Sommer. .4 rlirnrrl Lite ( New York. Iti lI 1 ; (Lido•. Iteddard, and other writers in the rum brill Vuturat tory (Lond(ln. IS95 19113).