206 
CLASS VI. 
that this animal, which he had found in a leaden gutter of his house, after 
it had been dried with the sand and other matters that adhered to it, 
revived again, when after two days he poured water upon it, which, having 
been previously boiled, could contain no living animaleule. He afterwards . 
found that the same phenomenon occurred after a lapse of five months 
(bl. 413). Different observers repeated these experiments. FonTraNna 
found Wheel-animalcules that had been dried for two years and a half 
revive on being moistened (Zraité sur le venin de la Vipéret., Florence, 
1781, 4to. pp. 90, 92), and SPALLANZANI saw the waking from slumber 
occur even after four years (Opuscules de Physique, tradwits par J. SENEBIER, 
Geneve, 1777, 11. p. 310). The last-named observer saw the same pheno- 
’ menon many times in succession ; nay, even eleven times he saw alternately 
apparent death and life. A few minutes are often sufficient to revive the 
creatures ; but such alone as were surrounded with sand and other matter, 
not those which lying quite bare had been dried, wererevived. Observations 
in the present century also are not wanting, by DuTROCHET, C. SCHULTZE 
(according to EHRENBERG on Philodina), and others. 
This phenomenon does not stand quite alone. We have spoken above of 
Anguillula (p. 194), and SPALLANZANI observed the same phenomenon in a 
microscopic aquatic animal, which he named Yardigrade, and which has 
been called Arctiscon by other writers. DusARDIN brings this and other 
similar animals as well as the. Wheel-animalcules into the same class of 
Systolides ; but we are of opinion that they ought rather to be placed, as 
very imperfect forms of Arachnoidea, with the Acari. It is on these tar- 
digrades that DoyGrE not long ago performed his very interesting experi- 
ments, and also, after most perfect desiccation of the animals when quite 
uncovered, succeeded in reviving them (Ann. des Sc. nat, 2® série, 1842. 
Tom. Xviil. Zoologie, pp. 8-— 35). 
To these observations no exception can well be taken; the facts must 
either be stoutly denied or be accepted as we find them. SPALLANZANI 
asserted incorrectly that life was quite gone, and that a real revival 
occurred (1, 1. p. 322). LEEUWENHOECK expressed himself more cautiously. 
BonneET too speaks of a seeming death, and says that life is not quite 
extinguished (Consid. sur les corps organisés, Cuvres, Neuchatel, 1779, 
8yvo. VI. p. 224, Contemplation de la nature, ibid. Tom. vitt. p- 262). Von 
HUMBOLDT calls the state of apparent death in these animals one of sleep, 
or of suspended life (Versuche iiber die gereizte Muskel-und Nervenfaser, 
1797. 8vo. I. s. 296). In this desiccated state life is potentially present, 
but does not announce itself by actual phenomena. If we choose to name 
this life Jatent, we must not call death itself a latent life ; certainly these 
animals are not dead, but their life is brought to a stand by the want of 
one of the most common and most necessary of vital stimuli, by the want 
of water. 
