322 TENACITY OF LIFE IN ROTIFER A. 



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 



