222 Causes and Course of Organic Evolution 



stimulation responses are indicated or definitely recognizable. 

 In the Caryophyta, while simple and direct responses to like 

 simple stimuli may occur, it often happens that a compounding 

 of two to five separate and successive stimuli, that all act on 

 some definite constituents of the living cell, gives rise to a 

 direct resultant response or rearrangement of the molecular 

 machinery of the cell, so that a pathway or line of action or 

 motion is proen\nroned intrinsically, before the organism 

 exhibits any evident intrinsic or extrinsic change. This may 

 be a resultant compromise or mean line, between the lines of 

 stimulation action, if the separate stimuli are all balanced in 

 strength relatively to each other, or it may in part or in whole 

 be in line with one only of the stimulation lines, if this exceeds 

 the others in strength. 



Throughout the animal series of the Caryota (Caryozoa) we 

 already have many interesting cases of resultant proenviron- 

 ment up to the Spongida and the Hydrozoa. But in the more 

 evolved genera of the latter, such as the Hydromedusa?, as 

 well as in the Anthozoa, the Echinodermata, most worms and 

 higher groups, there begin to appear new and special cell units, 

 the nerve cells, which become increasingly abundant and 

 complicated in their connections till we reach a climax in man. 

 These introduce, we would consider, a new and greatly more 

 complicating condition which we can now stay to consider, 

 before treating of the responses of the Metazoa* as a whole. 



It has been already explained (p. 88) that three probable 

 forms of life-energy already dealt with, the biotic, the cognitic, 

 and the cogitic, seem to be located respectively in the proto- 

 plasm, the nuclear-nucleolar substance or chromatin, and 

 the Nissl substance of the nerve-cell or neuratin, respectively. 

 So in the simplest living Acaryota the biotic energy of the pro- 

 toplasm acts, as above stated, so as to produce simple proen- 



* Here and subsequently we use the term Metazoa as including all nucleate 

 multicellular animal organisms; and its relation to unicellular and to non- 

 nucleate types is set forth in classification manner on p. ol thus: 



(a) Acaryozoa — Unicellular animals without cell nucleus. 



(b) Caryozoa — Unicellular or multicellular animals with cell nucleus. 



1. Protozoa — Nucleate unicellular animals. 



2. Metazoa — Nucleate multicellular animals. 



