24 ANDREWS. 



[53] Ectoderm with its products is but either repetition in 

 gross, or a multiplication by repetition, of causes and effects 

 which form the Protozoan ectosarc and its products. Beneath 

 the seeming demarcation of "germ layers" with their pro- 

 ducts, the substance expresses itself again, more definitely, in 

 a series of minute but kindred structural organizations of the 

 elements. These are to the substance as such what the germ 

 layers are to the substance as organism. There are through- 

 out the whole Metazoan organism countless areas of wide 

 range in size ; some restricted to the limit of single cells, 

 others passing through large numbers of these, some of most 

 minute vesicular structure, some having a beautifully marked 

 structure of Biitschli, or even coarser vesiculation ; but all 

 taking their rise from the general or "undifferentiated" proto- 

 plasm ; all functioning in a kindred way towards substance 

 environment ; and all true ectosarcal formations in origin, 

 structure, and activities. The same is true of endosarcal 

 areas, for these are found in strictly ectodermal regions and 

 cells of the organism. 



Physical nature heals the wounds of the living substance 

 with a frail pellicle of continuous substance ; physiological 

 nature supplements, or supplants, this as rapidly as may be with 

 a formation of ectosarc. In simpler and more primitive types 

 of organism this service is performed by interalveolar substance, 

 often aided secondarily by areas of Biitschli's structure. In 

 more stably and complexly organized, cellular types the same 

 surgical office is given by protoplastic activities of neighboring 

 cells; by wandering cells, as leucocytes, or migrating cells, and 

 as far as possible the damage is thus primarily repaired. 



By so much of experiment as was made, it is certain that 

 living protoplasm tends to protect itself, directly or indirectly, 

 by various devices from unsympathetic environment, albeit of 

 a kind never before experienced; and to protect its internal 

 environment from change thereby. Such devices are of a 

 nature which seals the substance for a time from intrusion of 

 adverse or disturbing conditions, and bar it in with its own 

 existing and intrinsic conditions acquired under more favorable 

 auspices. That is, the living substance shuts itself up with its 



