384 LOUIS MAX HICKERNELL. 



stices of a sponge, so water is held in every cell of the rotifer body. 

 It is hardly necessary to emphasize again in this connection that 

 such water is probably not held by capillary attraction as in a 

 sponge but by a loose molecular union. The presence of this 

 water in the rotifer tissues is demonstrable in a visual fashion, 

 for in the sections of normal undried rotifers the cells all possess 

 vacuoles between the granules or reticulum of the cytoplasm. 

 These vacuoles or spaces are certainly filled with the more fluid 

 cytoplasmic ingredients and their true fluid nature is demon- 

 strated upon examination of a section of a dried animal where 

 they have with few exceptions disappeared, or better still in an 

 animal recovering from desiccation where the former position of 

 granules of reserve food material is marked by vacuoles un- 

 doubtedly containing liquid. In a previous paragraph attention 

 was called to the fact that in those cells whose cytoplasm is 

 loosely granular in the normal condition, the granules were 

 closely packed in similar cells of a dried animal. The change 

 in space relation of these cytoplasmic granules is due to loss of 

 imbibed water. 



The amount of imbibed water which an organism may lose 

 and still live varies with the kind of organism. Seeds which in a 

 dormant condition contain from ten to not more than twenty 

 per cent, of water may still retain their viability and germinating 

 power if more than half of the water content is removed. This 

 viability of corn with different degrees of moisture content is 

 recorded by Babcock ('12) and I have repeated many of his 

 experiments and find them to be correct. 



In McDougal's cactus experiments it was found, as was before 

 mentioned, that loss of weight in full illumination may not 

 greatly exceed fifty per cent, of the water present without pro- 

 ducing death by desiccation. In seeds, on the other hand, a 

 loss of seventy-five per cent, of the water content need not 

 necessarily be fatal. and in some cases certainly the percentage 

 loss may be higher without death resulting. 



In Philodina, while exact quantitative measurements are 

 exceedingly difficult, the water loss judged by decrease in size 

 of the drying animal and by the nature of the dried tissues, 

 must certainly be higher than that of seeds. 



