6i6 



H. S. Jennings 



found by experiment to be true. When a .specimen undergoing 

 fission is pierced with the tip of the glass rod or otherwise muti- 

 lated, it does not go to pieces so rapidly as the adult, though in 

 most cases it finally disintegrates. But in a few instances speci- 

 mens thus treated survived. 



Thus, while the Paramecium ma was undergoing fission, its 

 anterior half ma^ was pierced with the rod, allowing a part of the 

 internal contents to escape. This half became distorted (Fig. 

 1 8, a) while the other half became swollen. The latter resumed 

 later its normal form, and fission continued. The injured half 

 a retained its distorted form (Fig. i8, b). During growth the form 

 becam'e somewhat nearer normal (Fig. i8, <?), but complete regu- 

 lation did not take place in this generation. 



Fig. 1 8 History of the specimen wa, mutilated during fission. See text. 



During the night the irregular individual divided. The anterior 

 product was quite normal in shape; the posterior one still showed 

 a slight irregularity of form at the posterior end. At the next 

 fission this disappeared and both products were normal. 



Thus the effects of the mutilation persisted in some of the indi- 

 viduals for three generations, then disappeared. 



In a number of other cases young or dividing specimens were 

 marked with deep furrows by pressing them with the rod. These 

 marks lasted some hours, but disappeared before the next fission 

 occurred. 



In the dividing specimen inb the posterior part mb^ was 

 pierced with the glass rod, so that a part of its contents escaped, 

 while by contraction most of the remainder of its contents were 

 forced into the anterior half mb^ (see Fig. 19, b). Thus the 



