3QO LOUIS MAX HICKERNELL. 



integration and absorption of the macronucleus in the cytoplasm. 

 Simultaneously a multiplication of the micro-nuclei is in progress. 

 Certain of the resulting micronuclei degenerate while the re- 

 maining one or two form the new macronuclear and micronuclear 

 apparatus. This results in the reorganization of the cell without 

 the fusion of two animals." They find not only that the re- 

 organization process is coincident with the low point between 

 rhythms but also that there is a causal relation between the 

 reorganization process and the rhythms. Woodruff defines a 

 rhythm as a minor periodic rise and fall in the division rate from 

 which recovery is autonomous. Woodruff believes that the 

 rhythmical changes which he describes are inherent in the 

 phenomena of the cell. There are changes in Paramcecium, 

 described by Calkins and others, involving a somewhat similar 

 reorganization of the cell but whose cause may be laid in part 

 to environmental conditions. 



The life history of Philodina consists in periodic increases and 

 decreases in activity as a result of environmental conditions and 

 in many respects its structural responses are similar to those 

 described by Woodruff and Erdmann in Paramcecium. The 

 environmental stimulus acting upon the rotifer to produce the 

 periodicity is dryness. The response to the stimulus is an inter- 

 action between nucleus and cytoplasm not unlike that taking 

 place in Paramcecium. Normal conditions of organization are 

 resumed as soon as the stimulus is removed and the noticeable 

 result of the entire process is an increase in reproductive activity. 

 Of course many of the physiological processes of the two animals 

 are markedly different in many respects and would not- admit 

 of close comparison but this one particular phase in which there 

 is such a marked agreement in the cytological phenomena accom- 

 panying a physiological state seems worthy of comment. 



The Relation between Desiccation and Reproductive Activity. 



It is hardly necessary to again call to mind the causal relation 

 between desiccation and reproduction in Philodina. The num- 

 erous observations of many authors has established this as a 

 fact. It is, however, profitable to speculate concerning the 

 specific cause of the increased reproduction. It is insufficient 



