440 Gary N. Calkins. 



spasmodic after prolonged captivity under a cover glass, and the 

 irregularity is an index of the ultimate disintegration. 



2. Structure of Paronicecium m Depression Periods. 



a. Starvation and its Effects. The periodic depressions which 

 were noted in the experiments, and which appeared at more or 

 less regular intervals (viz: about every six months) were note- 

 worthy because not always accompanied by the same type of 

 degeneration as that characteristic of starved forms. 



A most comprehensive study of the structures of starved Para- 

 mcecium was made by Wallengren, while various observers have 

 called attention to the characteristic vacuolization which the cell 

 protoplasm undergoes during starvation or at degeneration 

 periods in any culture. In general, Wallengren found that the 

 animals first use up the food material that is stored in granular 

 form, in the endoplasm, and that when this reserve is used, the 

 animals in lieu of other food, burn up first their endoplasm and 

 then the cortical plasm. There results from this destruction, 

 great vacuoles in the cell body which increase in size until the 

 entire organism is distorted through the pressure of one confluent, 

 or two or three great vesicles. Wallengren obtained his material 

 by transferring the Paramoecia to tap water again and again, and 

 thus ridding the medium of the customary bacterial food in a very 

 short time. My own experiments to this end consisted in leaving 

 the ciliates in a culture glass such as I have used throughout my 

 experiments, until all the bacteria had been eaten and the culture 

 medium had cleared. Thus a hundred or more individuals would 

 be left for a period of a month or six weeks in the culture chambers 

 where evaporation was prevented, and here they were watched 

 daily until they ultimately died of starvation. While Wallen- 

 gren's experiments were undertaken for the purpose of deter- 

 mining the efi^ect of starvation upon all of the protoplasmic 

 structures of these forms, mine were done for the purpose of 

 studying the effects of such treatment upon the nucleus and endo- 

 plasm, and general vitality. Wallengren found the following 

 effects in the protoplasm of Paramcecium after starvation for a 

 period of from 8 to lo days, which he designates as the "first 



