130 INDIVIDUALITY IN ORGANISMS 



have failed to reach any very satisfactory general inter- 

 pretation of them. Driesch, who has used Tubularia to 

 a large extent as experimental material, even maintains 

 that they cannot be interpreted on a physico-chemical 

 basis. As a matter of fact, however, not only do the 

 facts fall readily into line with the dynamic conception of 

 the individual which I have outlined, but many of them 

 constitute valuable evidence for that conception. 



I have found that previously existing metabolic 

 gradients in the stem of Tubularia are rapidly obliterated 

 and new gradients readily arise when metabolic con- 

 ditions change. This is due to the fact that the proto- 

 plasmic substratum is not very stable, and, except in 

 the hydranth, there is little structural differentiation 

 in relation to the metabolic gradient. Wherever the 

 stem of Tubularia is cut across, and even in many cases 

 where section is not complete, a metabolic gradient 

 arises in connection with the stimulation of the wound 

 and the open end exposed to sea-water and the oxygen 

 contained in it. The region of highest rate in this 

 gradient is at the cut end, and the gradient extends a 

 greater or less distance from the cut, according to the 

 physiological condition of the stem and the direction and 

 metabolic rate of the pre-existing gradient in the region 

 concerned. If the metabolic gradient resulting from 

 stimulation at the cut end is in the same direction as the 

 pre-existing gradient, then of course there is merely an 

 augmentation of the gradient, but if two gradients are 

 in opposite directions, as they are at the basal end of 

 a piece, they tend to neutralize, obliterate, or inhibit 

 each other, and the one which has the higher metabolic 

 rate sooner or later obliterates the other. The evi- 



