6o ANDREWS. 



substance of the Qg%. And it became evident that in the long 

 and intricate series of these phenomena, one must learn to 

 attach to each area in which is seen true organization, however 

 fleeting, of the elements, the value of a true physiological area 

 of the mass ; and to rank it as a true substance organ.^ 



The very transparent nature of the larval stages of starfish 

 affords large opportunity for study of the origin and primitive 

 nature of many later substance organs. In such transparent 

 forms as the Rotatoria one has an almost limitless source of 

 knowledge on these points. Other creatures yield still more. 

 From what is found in these, comes illumination for struc- 

 tures and processes less easily traced in less accessible proto- 

 plasm, which should enable us better to interpret results in 

 preserved material. 



[55] In all nervous or transmissive areas examined, was 

 found an organization strongly akin to that of contractile areas, 

 only still more emphasized in a peculiar way. The structural 

 characters here belong peculiarly to the finer foam, whether 

 the area involves a structure of Biitschli or not. Hence the 

 true nervous or transmissive substance forms fibrils of continu- 

 ous substance, which may be joined with, or woven into, any 

 amount of combination by other modified or unmodified trabe- 

 culae of the structure of Biitschli or of a coarser alveolar struc- 

 ture. Where these tissues are complex, the appearance given 

 by most reagents is singularly false, producing an unnatural 

 vacuolation which often simulates a beautiful, distinct structure 

 of Biitschli. 



[56] So far as I have seen in transparent aquatic creatures, 

 the termination of all nervous or transmissive areas is in the 

 continuous or interalveolar substance of a visible structure. 

 This does not, as will be shown, preclude possibility of invis- 

 ible filamentous extensions into alveolar inclusions, but all the 

 direct and indirect evidence is for a special modification of 

 the continuous substance simply ceasing at some given point 

 in this. 



The continuous substance is sometimes much swollen in 



1 See Activities — Cell-division, in this connection ; also New Formula for the 

 Living Substance, and Fosterhood. 



