Effects of Desiccation on the Rotifer 217 



Faggioli claim that the animals come from eggs concealed in the 

 sand in the dead bodies of the parents, the latter having of necessity 

 been killed by the exposure to the conditions of dryness. Another 

 body, represented by Leeuwenhoek, Ehrenberg, Pouchet, Davis, 

 and Hudson, although admitting that adult rotifers may survive 

 even prolonged conditions of desiccation, consider that they are 

 able to do so only in virtue of some effective means of preventing 

 the escape of water from their tissues, the condition of the animal 

 in the dried state therefore not differing in any essential respect 

 from its normal state. Still others, among them Spallanzani, 

 Schultze, Doyere, Gavarret and Preyer consider that the desicca- 

 tion is a true one and may continue theoretically up to a point of 

 absolute dryness without injury to the animal. They either state 

 specifically that the animal in this condition is lifeless or tacitly 

 assume such to be the case. Other observers, while admitting 

 that desiccation may proceed very far, consider that the hfe pro- 

 cesses never come to a complete standstill although they may be 

 very greatly retarded. 



It is the purpose of the present paper to consider the evidence 

 for these various views and to attempt to reduce the subject to a 

 state of greater certainty than that in which it now rests. The 

 two points which will chiefly be considered are first, whether or 

 not the animal suffers a true desiccation and, second, what is the 

 state of the vital processes of the Animal in the absence of water. 

 Before proceeding to the observations and experiments on which 

 the conclusions of the paper are based, a brief account will be 

 given of the structure, natural history, and behavior of Philodina 

 to render more intelligible that which is to follow. 



Ill STRUCTURE AND NATURAL HISTORY OF PHILODINA 



Philodina roseola is one of the commonest of the rotifers, be- 

 longing to the order Bdelloida of which the common rotifer. Roti- 

 fer vulgaris, is also a member. It is widely distributed through- 

 out the world, being frequently found in small basins in the rocks 

 in which water periodically collects; a favorite habitat is in the 

 stone urns in cemeteries. It is usually associated with the uni- 



