640 THE AMERICAX -X . / /rA'. /Z.AV7'. XXXVIIL 



having a striking resemblance to that of Difflugia. In place of 

 chloroform, linseed oil or other oils may be used. The drops 

 must then be injected into 70 '/ alcohol, since the oil would float 

 on water. 



The factors at work in the formation of the "artificial shells " 

 are diffusion currents within the chloroform, the adhesion of the 

 bits of glass to its surface, and the action of surface tension in 

 arranging and fitting together the bits of glass. Studies of the 

 process by which the shell of Difflugia is formed at the time of 

 division of the animal seem to indicate that the same factors 

 may be at work in the living organism. (See Rhumbler, '98, 

 p. 289.) 



Reviewing our results, we find that few of the experimental 

 imitations of the activities of Amoeba stand before a critical 

 comparison with what actually takes place in the animal. Such 

 comparison shows in almost every case that the factors at work 

 in the imitations are essentially different from those acting in 

 Amoeba. In particular, almost all the imitations based on local 

 changes in surface tension break down completely. 



What are we to conclude from this fact as to the part played 

 by surface tension in vital phenomena ? The tendency has been 

 of late to attribute more and more of a role among life processes 

 to surface tension. Amceba has been the chief place where the 

 important part played by surface tension seemed really demon- 

 strable ; the movements, the reactions to stimuli, the taking of 

 food, and the choice of food, were all attributed to this and 

 closely related factors. With the demonstration of the complete 



of surface 



for the phenomena 



were chiefly relied on to prove its importance, the supposition 

 that it plays an immensely important role in life processes loses 

 much of its weight. Surface tension may of course, in a more 

 refined way than was supposed for Amoeba, still play the large 

 role m vital phenomena that some attribute to it. In the 

 meshes of Butschli's protoplasmic meshwork, or in the muscle 

 fibnllx- (Bernstein), it may perhaps do what is demanded of it. 

 l ossibly the study of surface tension is still the most promising 

 held for detection of the physical factors underlying life proc- 

 esses. But the surface tension theory must come to us shorn 



