THE LIVING SUBSTANCE. 51 



specific contact as organs with external environment, are seen 

 instances of areal differentiation on an ectosarcal basis preceding 

 physiological function : of vesicular preformation of substance 

 organs before the actual opportunity for their use has arisen. 



Among the Metazoa such redistributions are common and 

 numerous in development of cells and organs. 



Within the endosarc of Amoebae and other Protozoans one 

 can see, fleetingly formed from moment to moment, small local 

 areas of true ectosarcal character ; that is, showing a uniform 

 distribution of the two sets of elements in relation to each 

 other, with homogeneousness of both in general character ; and 

 with certain organized, though fleeting, activities which are 

 characteristic of true ectosarc. Besides these, there are the 

 stable pellicular formations about nucleus and food sacs and the 

 contractile vesicle, which are all organized areas of interalveolar 

 stuff involving more or less of the structure of Butschli. Like 

 other contact areas, or substance organs, they are all charac- 

 terized by fluidity and uniformity of their inclusions. 



Such true and stable alveolar areas as are found in Protozoa 

 are, as a rule, marked by organized contractility, so that these 

 also are less expressive of physical form than of the correlation 

 with the foam structure of certain intrinsic powers of the 

 substance. 



With few exceptions, ectosarcal formations show with vari- 

 able intermission contractile activities. Even the nuclear 

 pellicle cannot be excepted, for few nuclei do not from time to 

 time have amoeboid changes of contour more or less marked. 

 Wherever in a Protozoan or Metazoan contractile activities 

 were visible as such, there was an organization of the elements 

 and structure typically ectosarcal, no matter how fleeting the 

 physiological manifestation might be. The structure might be 

 stable, or might not outlive the activity, but in all cases organ- 

 ization of the continuous substance upon a fluid-inclusion basis 

 existed at the moment of function in the functioning substance, 

 and was exactly of the sort seen in typical ectosarcal areas. 

 Wherever preparation of areas for organized contractile func- 

 tion was watched, the process was seen to be not other than 

 that typical of the formation of ectosarc. 



