DYNAMICS IN EVOLUTION. 77 



(Rciz), a word which to me has a very indefinite meaning. 

 The production of these blebs or incipient pseudopodia, which 

 I have often observed, and in a great variety of forms, may be 

 equally well explained by surface-tensional disturbance, the 

 viscosity of the plasma, etc., and not necessarily as caused by 

 a retreat of the substance toward the nucleus, as claimed 

 by Verworn, in order to receive a reinforcement or accession 

 of new nuclear molecules. 



The differentiation of the substance of an amoeboid, such as 

 A. protcus, into an outer hyaline layer and a central or medul- 

 lary part, the so-called " endosarc " and "ectosarc," is 

 again a purely physical phenomenon. The surface-tensional 

 forces must be exerted, for physical reasons, between molecules 

 of approximately the same dimensions, otherwise there could 

 be no tolerably coherent and stable outer stratum formed. 

 In other words, the molecules of the outer layers are recipro- 

 cally attracted to each other with a greater force at insensible 

 distances apart, than the larger and coarser particles are 

 attracted by the small uniform molecules at the same intervals 

 apart. The materials of an amoeboid are thus dynamically 

 sorted into two kinds, in virtue of their differences of attrac- 

 tion for one another. It thus comes about that " endosarc " 

 and "ectosarc" are merely names for the results of a 

 dynamical process that, so to speak, sorts the particles of 

 a living amoeboid into two kinds. The small surface-particles 

 or molecules necessarily attract each other under such condi- 

 tions of dynamical advantage over and above their attraction 

 for the larger particles, that the latter are constantly driven 

 inward and kept there for this reason. 1 In this case, again, a 

 morphological fact is only understood when subjected to 

 dynamical analysis. 



In this way one might go on and subject every detail of the 

 organization of an amoeboid to physical scrutiny, and show 

 that complex energy-combinations determined every detail of 

 its structure. Not a single amoeboid form that I have 

 yet encountered has failed to disclose this mechanical 

 and dynamical complex of agencies as factors competent to 



1 A geometrical diagram would be needed to make this statement perfectly clear. 



