290 C. M. CHILD. 



III. INHIBITION OF SENESCENCE BY PARTIAL STARVATION. 



If complete starvation and the resulting reduction bring about 

 rejuvenescence it should be possible by feeding animals enough 

 to prevent reduction but not enough to permit growth to keep 

 them indefinitely in practically the same physiological condi- 

 tion and so to prevent senescence. 



In 1911 a part of the stock used for asexual breeding was 

 isolated in the second asexual generation after collection and 

 the attempt was made to feed this stock only enough to maintain 

 the worms at approximately the same size. During the early 

 part of this experiment too much food was given and a few of 

 the animals underwent partial fragmentation and encystment. 

 All such individuals were removed from the stock and the ex- 

 periment was continued with the remainder, these being com- 

 pletely starved for several weeks after fragmentations occurred 

 in the stock in order to reduce their size and bring them back 

 into a physiologically younger condition in which fragmentation 

 would not occur. Since the early part of the experiment, the 

 food has been somewhat further reduced in quantity and no 

 further fragmentations have occurred. The stock was small 

 at the beginning consisting of some forty worms. Some of these 

 were lost by the early fragmentations and since that time animals 

 have occasionally crept out of the water and dried upon the 

 sides of the dish and others have been lost by being removed on 

 the pieces of food or have been accidentally poured out in chang- 

 ing water but there have been no deaths or losses from other than 

 these accidental causes. The stock now consists of five animals. 

 As regards feeding the procedure finally adopted and still adhered 

 to is to feed two or three times at intervals of two days, and as 

 soon as the animals begin to increase in size to stop feeding for 

 two or three weeks or until they are reduced to their former size. 

 In this way the animals have been kept during most of the two 

 years between four and seven millimeters in length. Whenever 

 individuals of the stock show more rapid growth or reduction 

 than the others they are isolated and fed or starved until they 

 are of the same size as the others when they are again returned 

 to the stock. During most of the time the stock has been fed 

 with pieces of earthworm, because experience has shown that 



