146 



SENESCENCE AND REJUVENESCENCE 



newly developed individuals are distinctly more susceptible than 

 the parents, i.e., they are physiologically younger. In the earlier 

 stages of the bud, however, while it is still attached to the parent 

 body and before it has developed the capacity for motor activity, 

 its susceptibility is not appreciably different from that of adjoining 

 regions of the parent body, or it may be even less susceptible than 

 these regions. 



The fact that the increased susceptibility appears only after 

 the asexually produced individual is separated from the parent 



L-i 

 Figs. 48, 49. — Two stages in the development of a bud in Hydra 



seems at first glance not to agree fully with the data and conclusions 

 from other forms, but this disagreement is only apparent, and re- 

 sults from the complication of the results by the factors of motor 

 activity and food. Motor activity of an individual, or even of a 

 region of the body in hydra, increases very considerably the sus- 

 ceptibility of that individual or region to cyanide. It is very 

 generally the case that the animals which show the greater motor 

 activity after being placed in cyanide die and disintegrate earlier 

 than the less active, and it has often been observed that marked 



