AMEBOID MOVEMENT 39 



the formation of ectoplasmic ridges, and so forth, found, upon 

 analysis, to resolve themselves into a large number of details 

 which differ more strikingly, the corresponding characters of one 

 from those of the other, than do the generalized characters of 

 which they are composed? 



These questions apply, of course, to all other organisms as well 

 as to amebas. Unfortunately, however, these questions are at 

 present unanswerable for all organisms. But for the amebas, at 

 least, the problem of form can be rid of some irrelevant matter 

 which, in numerous instances in the past, has been assumed to be 

 properly included. 



In the first place, changing a single character of the protoplasm, 

 such as the degree of viscosity, cannot explain the observed di- 

 versity of detail; neither can a variation of a number of the 

 physical characters of fluids produce such differences as are 

 observed in the dynamics of the different species of amebas. Our 

 whole experience with the fluids of physics speaks against such 

 an explanation. But, on the other hand, the invisible details of 

 structure of a fluid may become strikingly manifest under certain 

 conditions, namely, those surrounding the process of crystalliza- 

 tion. A slight change in the physical condition may produce a 

 considerable variety of crystal shapes, but this variety of shape 

 has nevertheless very definite limits which cannot be overstepped. 



Amebas like crystals are also most rigidly and definitely re- 

 stricted to a certain range of shape, which must be a direct re- 

 sult of the structure of the protoplasm composing them. Amebas 

 in fact are not any more "shapeless" than crystals are; and it 

 would be quite as exact to say that the crystals of water are shape- 

 less since a great variety of shapes are met with in snow, hoar- 

 frost, etc. The fact that corresponding parts of two species of 

 amebas resemble each other less and less closely as they are ana- 

 lyzed into smaller and smaller details, is in itself conclusive evi- 

 dence that the protoplasms of the amebas are chemically different ; 

 the resemblance between the gross anatomy and physiology be- 

 tween two different species is due to the greater conspicuousness 

 of such characters as are the result of the action of physical pro- 

 cesses. That is to say, chemically or molecularly different masses 

 of matter may resemble each other in their molar aspects. 



