210 Merkel Henry Jacobs 



enon of revival after desiccation in a particularly favorable way. 

 A limited number of observations were made on Adineta (Calli- 

 dina) vaga, a nearly related form, but these show practically no 

 points of difference from those made on Philodina. 



II HISTORICAL 



In the year 1701, Anton von Leeuwenhoek in searching for 

 new objects to examine under his microscope chanced to take 

 some of the dry dust from the gutter of a roof and on moistening 

 it was greatly astonished to see after a time living animals swim- 

 ming about actively in the water. Struck with the observation 

 he again allowed the animals to dry and on moistening them the 

 next day with water previously boiled by way of precaution against 

 introducing any life from outside sources, he obtained the 

 same result. Further experiments convinced him that these ani- 

 mals, which were rotifers, probably belonging to the species Roti- 

 fer vulgaris, might be deprived of water for at least several months 

 without losing the power of recovering their normal activities 

 when water was again supplied. This was the first observation 

 to be made on the phenomenon of desiccation with subsequent 

 revival in animals; strangely enough it attracted little attention at 

 the time. Leeuwenhoek beheved that the animals themselves 

 were not truly dried but that they were protected by an impene- 

 trable cuticle from loss of water * * * "cuticulas ex tam 

 solida conflatas esse materia ut ne miniman quidem permittant 

 exhalationem. Quod si sese aliter haberet, asserere non vereor 

 haec animalcula * * * onni aqua destituta necessario omnia 

 esse emoritura." 



The next mention of the subject was made in 1743 by an Eng- 

 Hshman, Turbervill Needham, who observed minute worms to 

 issue from grains of wheat when water was applied to them. To 

 use his expression they "took hfe" on the apphcation of moisture. 

 In the same year another Englishman, Henry Baker, again called 

 the attention of naturalists to the rotifers discovered by Leeu- 

 wenhoek, but he contented himself with merely repeating that 

 writer's description of them and it was not until ten years later 



