MORPHOLOGY AND PHYSIOLOGY OF GENUS URONYCHIA 379 



Starved cells 



Experiments on starved cells — table 11. When starved by being 

 placed in a poor food medium, U. setigera grows smaller, but 

 the protoplasm does not become vacuolated as does that of 

 Paramecium. Individuals will live for some time and even divide 

 if put into filtered sea-water, although the interval between 

 divisions is greatly increased. 



Experimental cuttings were made on individuals starved two 

 and four days, although not enough data were obtained to fur- 

 nish absolute evidence of the effects of starvation. It was soon 

 found that if put back into plain sea-water cut cells died with- 

 out regeneration, while if transferred to food media some would 

 live and divide, so this method was used in the experiments 

 performed. 



In all, thirty-seven cuttings were made. In twenty of these 

 experiments both fragments died at once. These are not listed 

 in table 11. 



Nine individuals were cut after two days of starvation. Both 

 pieces died in two of these experiments, although regeneration 

 took place in the larger micronucleate fragments. In the other 

 seven the parts with micronucleus regenerated and divided. 

 The amicronucleate parts died with no regeneration or with 

 very little. 



Eight individuals were cut after four days of starvation. In 

 five of these the small parts died at once or within a few hours 

 without regeneration, while the larger micronucleate fragments 

 regenerated even though they died without division. In one 

 case both fragments showed some regeneration, but died before 

 it was completed. In two experiments the larger pieces com- 

 pleted regeneration and divided, while the small parts died 

 without regeneration. 



Cutting cirri only 



In experiment no. 46, listed in table 4, by accident the posterior 

 cirri were cut off without injuring the body. Later the cell 

 was cut in the desired plane. However, it was noticed that 



