THE WEB OF LIFE 369 



of life began. Our hypothesis, based on many facts, is 

 that in this new world of life the complexifying tendency 

 continued, and we call that the self-differentiation of 

 protoplasm. Living creatures traded with time and found 

 fuller and fuller self-expression. No one doubts that many 

 kinds of ' flesh ' originated, one kind of fishes, another of 

 birds, another of beasts, another of man, as was said in 

 olden time. 



But we must add to this or superimpose on it another 

 idea, that the living creature is associative. We do not 

 wish to multiply formulse or mysterious tendencies, but 

 there seems to be a touch of protoplasm that makes diverse 

 creatures kin. A quaint instance may serve as a diagram. 

 In recently examining at Roscoff a large collection of the 

 little green worms known as Convoluta roscoffensis, Marcel 

 A. Herubel found among them about forty specimens of 

 Convoluta flavibacillum, a species which is not green, which 

 had not been previously noticed in this locality. The 

 peculiar fact was observed, that on the ventral surface of 

 each of them there was a young C. roscoffensis, clinging 

 on by its dorsal surface. When they w r ere separated 

 in the aquarium, they were re-united in half an hour ! 

 The meaning of the peculiar association remains quite 

 obscure, but, whatever it may be, the case may serve to 

 illustrate our idea, that many organisms go about with, 

 as it were, tendrils Unking themselves on to other organisms. 

 We have no great faith in the multiplication of ' tropisms ', 

 or inherent predispositions of organisms to move on certain 

 ways in answer to precise stimuli, but we would suggest 

 an addition to the list, viz. ' biotropism ' the attraction 

 of organism to organism. To rank this beside ' geotropism ', 

 ' heliotropism ', ' thigmotropism ', ' chemotropism ', and 



BB 



