Ti/pes Tardigrada and Rotifera. 27 



even be interrupted, and these little animals buried in appa- 

 rently dry dust, would stUl meet with sufficient humidity to 

 prolong their lives and to allow of reproduction, so that those 

 which have been supposed to become revivified would be in 

 reality, to use the expression of Ehrenberg, only the great 

 grand-children of those observed in the same material at the 

 commencement of the experiment. According to other na- 

 turalists, the desiccation of the sand or moss containing the 

 Rotifera, would infallibly kill the animals themselves, but 

 would not destroy the vital principle in the ova which they 

 may have deposited, and consequently, instead of witnessing 

 the resurrection of the animals themselves, we only see the 

 ova rapidly developed by the influence of the water, and giving 

 birth to animalculas whose growth would be equally rapid. 



Finally, there are other physiologists who consider that the 

 Rotifera, &c., of dry sand, do not undergo a complete de- 

 siccation, but such a degree of it only, as to plunge them into 

 a sort of torpor, and conceive that these animalculae, although 

 to all appearance dead, yet preserve a latent life, but still a 

 real life sufficient to establish a bond of connection between 

 the active life which precedes the evaporation of the fluids, and 

 that equally active, when they are restored by the addition of 

 humidity, to the full exercise of their functions. The obser- 

 vations of M. Doyere overturn all these hypotheses, and con- 

 firm, in the clearest way, the results obtained by Spallan- 

 zani. 



Thus, in answer to the arguments employed by Ehrenberg, 

 it is sufficient to observe, that living Tardigrada are never 

 found in the dry dust of gutters ; but that, by the aid of the 

 microscope, corpuscles can be seen which entirely resemble 

 the dead bodies of these animalcula?, deformed by desicca- 

 tion ; and that in matters where no living being was previously 

 discernible, living Tardigrada frequently appear on the addi- 

 tion of a little distilled water. M. Doyere is even assured 

 that it is not impossible to revivify these animalculae, if taken 

 one by one, and dried separately on pieces of glass, without 

 being surrounded by sand or other material, organic or inor- 

 ganic, capable of preserving them from the ordinary effects of 

 evaporation. In his experiments, he has been able to count 



