THE BIOLOGY OF THE CELL SURFACE 



tion derive their plausibility from their consistency with 

 known facts of cellular phenomena: one of these indicates 

 the elaboration of chromatin out of cytoplasm. More 

 than once have I in the foregoing chapters referred to the 

 origin and growth of chromatin out of the cytoplasm. On 

 the other side, there exist no data to indicate that chromatin 

 builds up c}'toplasm. 



The same emphasis that I place upon the differentiation 

 of ectoplasm out of the ground-substance in the genesis 

 of the primordial living thing, I place upon it as a cause in 

 the evolution of the animal and plant kingdom. 



Protozoa are classified into ascending orders on the basis 

 of their ectoplasmic structure and behavior. Eggs develop 

 into adults by virtue of ectoplasmic changes during differ- 

 entiation. Among multicellular adult organisms, grades 

 of complexity can be recognized : the more complex the 

 organisms, the richer are their modes of integration as 

 shown by comparative studies on nerve-systems. What 

 makes man's brain the greatest among animals, is not the 

 number of Its nerve-cells — indeed, in a given area, the pri- 

 mate brain has fewer cells than that of other mammals — 

 but the richness of their connections. Other forms of inter- 

 cellular integrations in multicellular organisms are also 

 ectoplasmic. 



Let us recall once more the fundamental functions of 

 living protoplasm. These are contraction, conduction, 

 respiration and nutrition. The primordial contraction, let 

 us say that exhibited by the egg or protozoan cell, involves 

 the cell interior to a secondary degree only. The cilia of 

 ciliated Protozoa are ectoplasmic structures. Muscle- 

 contraction in the highest organisms is a phenomenon of 

 the cell-surface.^ 



Also conduction, we found, is an ectoplasmic function. 

 The transfer of the effect of a stimulus is ectoplasmic, as 



1 Hill et al. 



358 



