DESICCATION IN PHILODINA ROSEOLA. 393 



Bachmetjew ('07) showed that juices of the insect body do 

 not completely congeal till they have been reduced to -- 4.5 C., 

 but at this temperature the insect does not yet die. 



Reiff ('09) kept an adult Actias selene at a temperature of 

 - 3 to - 6 C. from November 23 to January 3. Upon 

 raising the temperature to 17 C. the insect again became active. 

 The normal length of life of this species of Actias averages seven 

 to eight days. The total number of days which the two insects 

 experimented upon lived in an active condition was about two 

 days less than the average. 



Bachmetjew says that metabolism cannot take place in a 

 frozen insect because it is impossible for the blood to circulate. 

 However this may be, we have shown that metabolism takes 

 place in the dried rotifer in the absence of a circulating fluid. 

 Furthermore the experiments of Reiff just mentioned show that 

 the total length of life is lessened in an insect when freezing 

 intervenes. This strongly suggests that the life processes go on 

 slowly here also. It seems desirable that the question of struc- 

 tural changes and metabolic processes during freezing among 

 certain animals should be carefully investigated. 



V. SUMMARY. 



1. The tissues and the parts of the individual cells of a desic- 

 cated Philodina roseola maintain their identity during the 

 drying process. 



2. No protecting membrane is secreted when drying begins 

 or at any other time during the desiccation process. The 

 integument of the dried rotifer is thinner than that of the undried 

 specimen. 



3. Metabolism goes on slowly in the dry condition as is evi- 

 denced by changes in the walls of the digestive tube. 



4. Desiccation in Philodina may be complete but not absolute 

 without fatal results. 



5. The typical nucleus in all the tissues of Philodina consists 

 of a single large karyosome surrounded by a clear space with a 

 distinct nuclear membrane at the periphery of the clear space. 



6. The general effect of desiccation upon the cells of the rotifer 

 tissues is the production of a nuclear-cytoplasmic rearrangement 



