THE LIVING SUBSTANCE. 23 



between actual lines and included spaces. Further " network " 

 ill expresses a structure existing in three dimensions of space. 



I shall therefore restrict the use of this word to the optical 

 network effect, whether this at the moment expresses a physi- 

 cal fact or an optical figure ; and also, when not otherwise 

 specified, to mean the intersecting lines of this, excluding 

 interspaces. 



By contimcozis substance will be meant the whole substance 

 separating inclusions — that is, it will be used in the strict 

 physical sense. 



Interalveolar sUiff, or material or foam, or substance, or pro- 

 toplasm, will be used for the continuous substance, exclusive of 

 the actual alveolar lamellce : and ijiteralveolar structure, as de- 

 scriptive of the distribution of the two sets of elements in this 

 material. 



, By this phraseology, which will presently be seen to be very 

 necessarily precise, many mental difficulties and much vague- 

 ness are evaded in dealing with protoplasmic foams. 



CONTINUOUS SUBSTANCE. 



Our conception of the lamellar substance of Butschli's struc- 

 ture being enlarged by knowledge of the finer froth structure 

 within it, we must now image to ourselves the true continuous 

 substance as forming the lamellar and also interalveolar stuff 

 of the finer foam ; then, as being continuous by way of these 

 with the lamellas and interalveolar stuff of Butschli's structure ; 

 then, by way of these, continuous with all pellicles internal 

 to the mass ; and finally, in the same manner, continuous with 

 the external, or mass, pellicle and its products. 



This state of things can be seen in many transparent areas, 

 and in some entire masses of protoplasm. Those optical appear- 

 ances, upon which objection to the fluid foam structure of proto- 

 plasm has been based, such as fibrils and networks of indubi- 

 table firmness, are here for the moment set aside, as, though 

 their existence will later be finally proven, they will also be 

 shown to be coexistent with, and in no sense inhibitive of, a 

 true foam state. 



