386 LOUIS MAX HICKERNELL. 



which are an integral part of, or are merely inclusions in the 

 tissues have their molecular structure broken up into newer 

 forms of a lower order. In this w r ay energy is derived from 

 food material and life may be prolonged for a greater or less 

 period of time depending upon the amount of reserve material 

 present. 



Both types of chemical reactions outlined above are hydrolytic 

 processes. This means then that metabolic water is being 

 evolved in small quantities during the entire dry period. 



It should be understood here that the processes just outlined 

 are hardly possible of actual demonstration for if they are suf- 

 ficient to keep such a small organism as a rotifer living for years 

 in the dried condition they must of necessity be exceedingly 

 slow. Observations made by Babcock ('12) show that respira- 

 tion and consequent oxidations in seeds and spores are practically 

 suspended, it being possible to detect them only by observations 

 extending over long periods of time. If this be true of an em- 

 bryonic structure with its simple organization it is true to a 

 greater degree in an adult animal in a state of retarded activity. 



Death ensues in all dormant organisms at the end of a certain 

 time. The period of dormancy is limited. In Philodina, since 

 metabolism proceeds continuously but slowly as I have shown, 

 the death of an animal can be attributed to starvation rather 

 than dryness. Dryness is a contributing cause of death but the 

 animal dies as a result of lack of food rather than as a result of 

 lack of moisture. 



We may briefly summarize the previously mentioned causes 

 of death in the dried rotifer as follows: (i) Mechanical injury 

 due to too rapid drying, (2) starvation resulting from lack of 

 reserve food material, (3) poisonous effect of metabolic products 

 and (4) insufficient time before drying to effect the nuclear- 

 cytoplasmic reorganization. 



The Significance of the Nuclear- Cy to plasmic Interchange During 



Desiccation. 



The nucleus in the cells of most of the tissues of P. roseola con- 

 sists, as was pointed out before, of a single large karyosome 

 surrounded by a clear area and having for its boundary a definite 



