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-difierentiation of 

 protoplasm. Living creatures traded with time and found 

 fuller and fuller seK-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 Hving creature is associative. We do not 

 wish to multiply formulae or mysterious tendencies, but 

 there seems to be a touch of protoplasm that makes diverse 

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

 In recently examining at Koscoff a large collection of the 

 little green worms known as Convoluta roscoffensis. Marcel 

 A. Herubel found among them about forty specimens of 

 Convoluta flambacilhim, a species which is not green, which 

 had not been previously noticed in this locaUty. The 

 peculiar fact was observed, that on the ventral surface of 

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

 on by its dorsal surface. When they were 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 hnMng themselves on to other organisms. 

 We have no great faith in the multiphcation of * tropisms ', 

 or inherent predispositions of organisms to move on certain 

 ways in answer to precise stimuh, but we would suggest 

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

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

 ' hehotropism ', ' thigmotropism ', ' chemotropism ', and 



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