228 Causes and Course of Organic Evolution 



these, and then radiate definite tubes of energy to definite 

 and appropriate areas of response in the organism, became 

 by degrees an estabhslied and ever more complex feature of 

 evolving animals. 



In seeking now for a morphological and physiological con- 

 tinuity between higher Protozoa and simpler Metazoa, from 

 the proenvironal standpoint, the writer believes that such 

 can be established if it be accepted that durmg mid-archsean 

 times a group of organisms existed that were somewhat inter- 

 mediate between a ciliate infusor and a primitive rotifer. This 

 probably resembled much the embryonic stage of Callidina as 

 described and figured by Zelinka. 



Here extremely delicate division walls early differentiate 

 the egg into a set of biotic-cognitic cells that functionally 

 correspond to the trophonuclear constituent in haemoflagel- 

 lates, and the meganuclear constituent in infusors, with their 

 associated protoplasms. Such cells become the main mass 

 of the epiblast and hypoblast, including the alimentary canal, 

 the muscular tissue and gland cells. Next, and almost simul- 

 taneously, the nervous system originates as an anterior multi- 

 plication of epiblast cells, that in position and future energizing 

 relation recall the anterior motile nuclear part of a haemo- 

 flagellate. Further the deeper hypoblast forms a medio- 

 posterior cell-mass that becomes the primitive gametic con- 

 stituent of the organism. 



From later mid-archsean days on to the present time myriads 

 of types doubtless lived, that must perfectly have filled up 

 the gap between existing ciliate infusors, on the one hand, 

 and embrj^onic rotiferan types, on the other, and which in 

 graded manner must have united unicellular organisms pos- 

 sessing bio-cognitic, cogitic, and gametic or hereditary con- 

 stituents, with simple multicellular ones in which these became 

 loosely separated entities as in rotifers now. 



Alike the cogitic or nerve cell substance and the gametic 

 or hereditary cell substance of primitive metazoans probably 

 represents greatly more complex and energized chemical com- 

 pounds than do the biotic or protoplasmic, and the cognitic 



