C. M. CHILD. 



Series 56 /, October 12, IQII. Ten worms full grown but still 

 dark in color and still feeding. Body cut into four equal pieces, 

 a-d. Table VIII. gives percentages of encystments. 



TABLE VIII. 



No Encystment. Encystment. 



a 60 40 



b 100 



C 100 



d ioo 



Series 58 /, October 13, IQII. Ten worms, full grown, gray in 

 color and no longer feeding. Body cut in four equal pieces, 

 a-d. Table IX. gives percentages. 



TABLE IX. 



No Encystment. Encystment. 



a ioo 



b ioo 



c ioo 



d ioo 



The older worms show the greater frequency of encystment of 

 pieces. The same results have been obtained in other similar 

 series without exception. 



5. The Physiological Condition of Animals Reproduced from 

 Artificially Isolated Pieces. 



The animals reproduced from pieces isolated by section are 

 physiologically young, whether a period of encystment occurs or 

 not. In this respect they are similar to the worms produced 

 from the pieces which separate and encyst naturally. Small 

 pieces cut from the bodies of old worms and allowed to repro- 

 duce whole animals show the same differences in rate of metab- 

 olism from old animals as the worms emerging from cysts 

 naturally produced. The differences in susceptibility to cyanide 

 are essentially the same as in Table I. Moreover, these small 

 worms arising from pieces of large old worms are capable of 

 rapid growth if fed and of repeating the life cycle. As they grow 

 the rate of metabolism, as indicated by their susceptibility to 



