Stndirs on Rrgiilntifjii 389 



In these pieces then, akhough there is no other visible reguhi- 

 tion except wound-closure, the original intestinal branches undergo 

 complete degeneration and a new set of shorter and more slender 

 branches develops in their place. Moreover, the development of 

 new intestinal branches occurs only after two or three months, 

 during which time the pieces have undergone considerable decrease 

 in size. Evidently it is not correlated with other processes of form- 

 regulation in these pieces. 



These remarkable phenomena seem to me to constitute a prac- 

 tical demonstration of the hypothesis which has served as the basis 

 for interpretation of the other phenomena of intestinal regulation 

 in this species. As a matter of fact they play an important part 

 in the development of the hypothesis in my mind. A brief dis- 

 cussion will serve to show clearly their correlation with mechanical 

 conditions. 



In the first place muscular activity is relatively very slight in 

 these pieces, consequently the movements of the intestinal contents 

 are also relatively slight. Under these conditions the intestinal 

 contents accumulate, as can readily be observed, in the axial 

 intestine and enter the branches but little, except when more 

 powerful contractions are induced by artificial stimulation. The 

 old intestinal branches, not being adapted to these conditions, 

 undergo very rapid degeneration and only the axial intestine 

 remains. The persistence of this part of the intestine is to be 

 expected, since all muscular contractions cause movements of its 

 contents, and since these are accumulating as time goes on. 



These pieces require little nutrition in consequence of their rel- 

 atively slight activity, hence the products of degeneration do not 

 undergo resorption as rapidly as they are formed, but accumulate 

 in the intestine to such an extent that they distend it greatly, and 

 finally bring about the formation of a new set of intestinal branches, 

 which are adapted to the new conditions, and which undergo 

 gradual reduction as these conditions change in following stages. 

 Only in pieces where the axial intestine becomes distended with 

 the products of degeneration do these new branches appear. In 

 general, as the length of the piece decreases, the rapidity of degen- 

 eration of the old branches increases and the distension of the 



