346 LOUIS MAX HICKERNELL. 



envelope before the last traces of moisture on the slide disap- 

 peared. This conception has been widely accepted by many up 

 to the present day. 



Zacharias (1886) and Faggioli (1891) both reverted to the view 

 of Bory St. Vincent that the supposed revival was due to the 

 hatching of eggs concealed in the sand. 



From the time of Faggioli's paper until 1909 no conclusive 

 work on the subject of desiccation appeared. It will at once 

 be seen that the main questions involved in the desiccation prob- 

 lem had not been solved. In 1909 Jacobs, working upon Philo- 

 dina roseola attempted to determine the real conditions attending 

 the drying process. 



Jacobs outlines the questions involved in the desiccation prob- 

 lem as follows: "What is the actual effect of drying on a rotifer? 

 Is the water really removed? Does the animal secrete a pro- 

 tecting membrane? If the animal actually dries what is the 

 condition of its tissues? Are life processes at a standstill or 

 are metabolic activities going on all the time in a reduced state?" 



Jacobs concluded because of the shrinkage in the tissues, be- 

 cause of negative results in physical and chemical tests for water 

 in the dried animal and as a result of other indirect methods, 

 that the rotifer body becomes truly desiccated. He found no 

 evidence of a waterproof cyst. His answer to the question 

 regarding the condition of the tissues in the dried animal was not 

 very definite, at least not complete, and this for the very good 

 reason that he made no cytological examination of the tissues of 

 the dried rotifers. Jacobs decides that the metabolic changes 

 probably continue in the tissues of dried rotifers. 



In all the discussion and observation upon the subject of desic- 

 cation phenomena previous to the publication of the preliminary 

 note on this work, apparently no one had considered the problem 

 from a cytological point of view. This is true not only of the 

 study of animal tissues, but among plants as well. Certain algae, 

 pteridophytes and liverworts can be dried and will subsequently 

 recover. This fact has been known for years. Pfefter (1903) 

 comments upon physiological phenomena attending desiccation 

 but mentions no changes in structure. The author published 

 in 1914 a preliminary account of the observations recorded in 

 this paper. Brown (1915) working with McDougal at the 



