226 Aierkel Henry 'Jacobs 



is extended, often with great suddenness. This is apparently 

 accomplished by the contraction of the circular muscles of the 

 body which thus set up a pressure which causes it to be protruded. 

 Even in individuals which have been killed by drying the foot 

 becomes more or less extended but this is probably due to the 

 absorption of water by osmosis. 



After the first extension of the foot, movements separated by 

 periods of rest may recur at intervals for some time before the 

 animal fully recovers and creeps away. Complete recovery some- 

 times occurs in as short a time as ten minutes, but under certain 

 conditions it may require several hours or even a day. Most 

 workers have introduced a source of error into their observations 

 by failing to keep their rotifers for a long enough time. In the 

 present series of experiments, the animals were always kept at 

 least twenty-four hours before being pronounced dead. 



After the rotifers have recovered they may show the effects of the 

 desiccation in various ways. Sometimes the body is more or less 

 crooked and distorted, at other times the cilia appear injured and 

 do not beat normally. In other cases the animals remain con- 

 tracted and make no movements although they are not dead as is 

 shown by the fact that they undergo no disintegration. That 

 some of the hfe processes such as oxidations still continue may be 

 shown by placing upon them a drop of a solution of neutral red 

 which has been rendered weakly alkaline by a very small quantity 

 of sodium bicarbonate. Living rotifers which are excreting car- 

 bon dioxide change the color of the solution and are rapidly stained 

 pink or red; dead ones do not show this reaction. A complete 

 transition is therefore shown from individuals which are killed 

 through those in which movements never appear but some of the 

 life processes continue for a short time and those which have been 

 more or less injured to those which completely recover and show 

 no visible signs of injury. 



The facts just mentioned may be considered as an answer to the 

 views of those who doubt the whole phenomenon of recovery after 

 desiccation, among whom Zacharias ('86), Fredericq ('89) and 

 Faggioli ('91) may be named as some of the more recent workers. 

 The evidence advanced by these men is purely negative in char- 



