172 
POPULAR SCIENCE REVIEW. 
the reviviscence of the young of Tylenchus tritici. To ascertain 
the effect of different degrees of desiccation, young Tylenchi^ 
three years old, were taken and placed under the receiver of 
an air pump, together with a large capsule containing con- 
centrated sulphuric acid, to absorb all aqueous vapour; the 
air was then exhausted, and the animals allowed to remain in 
vacuo for five days. When withdrawn and immersed in pure 
water, most of them resumed their activity after a period of 
three hours. Subsequent experiments convinced him that larvae 
varying from one to three years old, invariably recovered as 
quickly after they had been completely desiccated by a sojourn 
of five days in a vacuum, as did others of the same age which 
had merely been exposed to the air for a similar period. Davaine 
found these animals irreclaimably lost their vitality when sub- 
mitted to a dry heat of 160° F., though their power of resisting' 
low temperatures was most remarkable : they recovered all their 
vital manifestations after having been subjected to the intense 
cold of 0° F. for eight or ten hours. 
The experiments which have been conducted by MM. Doyere 
and Gravarret* upon the degree of tenacity of life possessed by 
the Kotiferse, ‘‘ Sloths,” and Anguillulidse found in tufts of moss 
are of the most interesting description, and were conducted with 
the greatest care and caution. Some of the startling results at 
which they arrived may be appreciated by the brief narra- 
tion of one experiment destined to test the power of resisting 
simple desiccation at ordinary temperatures possessed by these 
animals. Portions of moss which had remained sixty-seven 
djays in a cabinet^ %vere submitted for two days to the in- 
fluence of dry air^ and during fifty-one days to the action 
of a vacuum. The mosses then became so completely dried that^ 
after four d.ays of exposure to the double influence of a vacuum 
and sulphuric acid, they underwent not the slightest diminution 
in weight, and yet, after twenty -four hours of simple moistening- 
ivith water, the rotifers, the sloths and the Nematoids had 
completely regained their activity. Unfortunately, other inter- 
esting results arrived at concerning the influence of heat upon 
previously-desiccated animals, refer to the two former varieties 
only, since no Nematoids, either living or dead, were seen in 
these later experiments. The Eotifers and Sloths,” however,, 
recovered after having been submitted for a few moments 
to a dry heat of more than 212° F. 
It was first observed by Spallanzani that one of the essential 
conditions for the revival of these animals found in tufts of 
moss was, that their period of desiccation should either be 
passed in the tufts, or else that during this time, their bodies 
* Arm, des Sc. Nat. 4me Ser. t. xi, 1859, p. 319. 
