322 TENACITY OF LIFE IN ROTIFERA. 



859. The capability which these Animalcules possess, of 

 being revived, after having been entirely dried up, or desiccated, 

 is one of the most curious points in their history ; since no other 

 animals of an organisation so complex, appear able to preserve 

 their vitality under the same treatment. The fact was first 

 observed by Leeuwenhoek ; and it has been since confirmed by 

 other observers. Ehrenberg doubts, however, whether a com- 

 plete desiccation could have taken place ; thinking it impossible 

 that the animal should survive it. The following statement of 

 my own experience on the subject may not, therefore, be unde- 

 sirable. In the summer of 1835 I placed a drop of water, con- 

 taining a dozen specimens of the Rotifer vulgaris, on a slip of 

 glass ; and allowed the water to dry up, which it did speedily, 

 the weather being hot. On the next day, I examined the glass 

 under the microscope, and observed the remains of the animals 

 coiled up into circles. a form which they not unfrequently 

 assume when alive, but so perfectly dry that they would have 

 splintered in pieces if touched with the point of a needle, as I 

 had before observed in similar experiments. I covered them 

 with another drop of water ; and in a few minutes ten of them 

 had revived, and these speedily began to execute all their regular 

 movements with energy and activity. After they had remained 

 alive for a few hours, I again allowed the water which covered 

 them to dry up ; and I renewed it on the following day with the 

 same result. This process I repeated six times ; on each occasion 

 one or two of the animals did not recover ; but two survived to 

 the last; and with these I should have experimented again, 

 had I not accidentally lost them. It is possible that the species 

 on which Ehrenberg and other foreign naturalists have experi- 

 mented, may not be the same as that which I and other English 

 observers have used. Something, too, appears to depend upon 

 the season and the general condition of the animal ; for, on 

 repeating the experiment in subsequent years, I have found the 

 results extremely variable, not more than one or two sometimes 

 recovering, out of a large number that had been dried up. It is 

 interesting to remark, that, whilst, in the embryo which is being 

 developed from the egg, the rotatory and masticating organs are 



