LEEUWENHOEK 215 



superficially dried, transported by wind or flying animals, 

 and afterwards revived by moisture, explained many of 

 the cases which had been thought to prove the genera- 

 tion of animals from putrid matter. 



The means employed by gutter- rotifers to protect 

 their bodies from complete desiccation are more elabo- 

 rate than Leeuwenhoek was aware of They not only 

 contract their bodies, but seal up the ends with gelatinous 

 plugs ; if the process of drying is too rapid for this, as 

 for instance when naked rotifers are dried on a glass 

 slip, they perish at once. It has been found possible, 

 by placing strips of paper in a wet gutter, to procure 

 groups of rotifers glued to one another and to the paper, 

 as many as a hundred together. When thus protected, 

 they show remarkable power of resisting extremes of 

 temperature ; they can also endure the vacuum of an 

 ordinary air-pump, though not the more complete 

 exhaustion of the Sprengel pump, and they revive 

 after drying in vacuo over sulphuric acid.^ 



Long after Leeuwenhoek's death Spallanzani ^ showed 

 that the moss-haunting Tardigrades exhibit the same 

 power of enduring superficial drying ; so do Infusoria 

 and other Protozoa, moulds, bacteria, seeds and eggs. 

 Preyer has compared the organism whose life is thus 

 temporarily arrested to a clock which has been wound 

 up and then brought to a stand ; a push is enough to set 

 it going again. But an organism which has once been 

 thoroughly dried is like a clock whose spring is broken. 



In his Royal Society papers Leeuwenhoek describes 

 and figures Limnias ceratophylli and Melicerta ringens." 



iH. Davis, Monlh. Micr. Joum., 1873, p. 287; Hudson and Gowe, Vol. I, 

 p. 95 ; Hartog, Camb. Nat. Hist., Vol. II, p. 227. 



2 OpuacvleH de physique animale et v^gStale (1776). 



» Phil. Trans., Noh. 295 (1706) and 337 (1713). In 1713 the natumliHt niuBt 

 have been over eighty years of age. 



