192 C. M. CHILD 



placed in the KCN, while the worms of Lot 2 remain intact in 

 most cases longer than those of Lot 1 and require four and one- 

 half hours to reach Stage V. 



That the rate of reaction is higher in the more recently hatched 

 worms cannot be doubted. They are more active and grow more 

 rapidly than the older worms and there is not the slightest reason 

 to doubt that if we could measure their metabolism directly, as 

 has been done for higher animals, we should find that they, like 

 the young of higher animals, show a higher rate of reaction per 

 unit of body weight than the older animals. 



The following simple experiment also indicates that the rate 

 of reaction in the young worms is higher than that in the old. If 

 a miscellaneous stock of several hundred worms, including both 

 young and old is placed in water in an Erlenmeyer flask, which is 

 then tightly corked, the worms begin to die within a few hours 

 and it is always the young worms which die first. That death 

 in this case is due to lack of oxygen rather than to the presence of 

 CO2 or other products of metabolism is indicated by the fact 

 that the water from such a flask in which worms are dying rapidly 

 will not kill other worms, provided they have access to a small 

 bubble of air. The effect of KCN 0.001 m. is almost exactly simi- 

 lar to that of lack of oxygen: in both cases the worms with the 

 higher rate of reaction (the young worms) die first. 



The possible objection that the smaller size of the younger 

 worms may in some way determine the result is met by the 

 following facts: the younger worms do not simply disintegrate 

 faster than the older, they begin to disintegrate earlier; it is diffi- 

 cult to see how difference in size alone can account for this differ- 

 ence. Secondly, in certain experiments on nutrition to be de- 

 scribed elsewhere, the larger worms disintegrate earlier than the 

 smaller, because of a higher rate of reaction resulting from a differ- 

 ent nutritive condition. In fact a large number and variety of 

 experiments to be described will demonstrate beyond a doubt 

 that size alone is a factor of comparatively little importance. It 

 is, in fact, one great advantage of the method that it is at least 

 very largely independent of size. 



