DESICCATION IN PHILODINA ROSEOLA. 365 



ness. This would be expected in a non-protoplasmic structure. 

 The hypodermis, however, which in the undried animal is from 

 two to four times as thick as the cuticle, has shrunk until it is 

 scarcely thicker than the cuticle itself. The nuclei do not 

 shrink perceptibly but cause swellings on the hypodermis at 

 the points where they occur. I have examined sections of 

 hundreds of specimens dried in various ways and know that this 

 is the characteristic condition of the integument of the dried 

 rotifer. I believe that these observations should effectively 

 dispose of the arguments of those who maintain that the drying 

 animal secretes a water-proof cyst for protection during the dry 

 periods. 



In the vitellaria the drying process affects the cytoplasmic 

 portion in less striking fashion than it does the nuclei. The 

 granular material of the cytoplasm appears almost the same as 

 in the undried organs. The spaces between granules are less 

 noticeable. These spaces are probably filled with cell-sap in 

 the active animal and it is to be expected that with loss of water 

 they will largely disappear, permitting the more solid granules 

 to pack closely together. The membrane surrounding the vitel- 

 larium and ovary shows no marked change. It is of practically 

 the same thickness and consistency in the dried as in the undried 

 animal. 



In the nuclei of the vitellarium noticeable changes have oc- 

 curred. As was stated before, a section of the nucleus in the 

 vitellarium of an undried animal shows a central, densely staining 

 karyosome surrounded by a clear space, and around the clear 

 space a definite, but not usually thick, nuclear membrane. The 

 nucleus in the dried vitellarium loses, for the most part, its 

 affinity for stains. The karyosome may entirely disappear but 

 usually there are remnants of it distributed here and there 

 through the nuclear space. Taking the place of the karyosome 

 is a more or less regular reticulum which reaches to the nuclear 

 wall. The latter has become thickened during the process of 

 drying; whereas in the nucleus in the undried condition the 

 densely staining material was aggregated in the center and the 

 clear area around the periphery, in the nucleus in the dried 

 condition these relationships are just reversed. What remains 



