THE BIOLOGY OF THE CELL SURFACE 



location enclosing a vacuome. Thus, respiration may 

 have determined the difference between animal- and 

 plant-nutrition. 



Animals evolved slowly or rapidly, farther and farther, 

 depending upon the degree to which ectoplasmic behavior, 

 Its faculty for contraction and conduction, developed. The 

 greater became these two forms of behavior, the more 

 Imperative became the need of exquisite means for respira- 

 tory-exchange. Respiration, according to our assumption, 

 played a part in establishing the difference between anlmal- 

 and plant-nutrition. Animal nutrition advanced showing 

 progressively increased utilization of large surface-areas for 

 the play of reactions — in digestion and for absorption of 

 the digested end-products. With this evolved in increasing 

 complexity a circulating system which gained steadily in 

 structural perfection whilst its correlation with the respira- 

 tion-system increased; and a more exact Integration by 

 nerves and finally by Internal secretions arose. 



Thus all forms of behavior by which we recognize that 

 a thing is alive express themselves In response to the envi- 

 ronment in the activity either of the ectoplasm itself — 

 as in unicellular organisms — or of structures which are rich 

 In ectoplasm. The fineness and nicety of ectoplasmic 

 organization Increase progressively in the animal kingdom 

 from the lowest to the highest organisms and thus parallel 

 the course of evolution. This course, from the emergence 

 of life out of non-life to the separation of animals from plants 

 and farther to the unfolding of progressive complexity of 

 animal-form, makes manifest the role and Importance of 

 the ectoplasm in evolution.^ 



This hypothesis of the evolution of the living world holds 

 also for the more restricted problem of evolution, the 

 origin of species. As I see it, the most valid criterion for 



1 Just, 1933 a. 



360 



