THE LIVING SUBSTANCE. 6 1 



single or isolated fibrils, tapering down towards its termination 

 in the continuous substance to a less and less perceptible 

 filament which clearly must end in the continuous element 

 of the finer structure of the interalveolar foam. In other 

 instances the fibril, or nerve line, of continuous substance is 

 uniform in width throughout its entire length. The walls of 

 the vesicles in most transmissive areas seem relatively very 

 thick with regard to size of inclusions. In some ganglia 

 examined the vesicles were, per contra, large with thin walls, 

 and the whole area had a spongy appearance. Transmissive 

 inclusions appear to be homogeneously fluid, like those of all 

 true ectosarcal formation. 



Between the sacs in which lie the nematocysts of Hydra, were 

 seen delicate lines of alveoli which connected these in groups 

 of variable number. The alveolar lines were in direct continu- 

 ity, as to their continuous substance, with that of the alveolar 

 pellicles forming the sacs. The optical aspect of the lines, 

 which are to be resolved by the highest powers only, is exactly 

 that of such areas as form the skin nerves and other fibrillar 

 nerves in rotifers, etc. Watching a Hydra under stimulation, 

 those groups of cysts between which I could trace this living 

 connection, seemed to coordinate during discharge of nemato- 

 cysts from that portion of the animal. 



[57] In such transmissive areas I have seen no direct evidence 

 of contraction, but that does not by any means negate the possi- 

 bility of such.i 



[58] Transmissive areas seem to be very stably organized in 

 the cases where they appear as special protoplasmic structures. 



[59] It must be noted here that all ectosarcal formations are 

 highly transmissive in an organized manner ; differing in the 

 matter and manner of transmission according to their specific 

 structure. Wherever there is organized contraction there is 

 also a certain sensitive transmissiveness which seems to be 

 inseparable from such organization of the elements in homo- 

 geneous and specially continuous manner, and without breaks 

 in the general state of the continuous element. 



[60] In all ectosarcal formations which show marked struc- 



1 See Contractility. 



