212 CLOSE OF THE PRE-EVOLUTIONARY PERIOD 



logical rather than morphological. The distinction which he 

 draws between the sensory and trophic layers on the one 

 hand, and the motor-germinative layer on the other, is 

 entirely a histological one. The greater part of his book, 

 indeed, is devoted to a study of the histogenesis of the 

 different organs of the body ; he is bent chiefly upon 

 unravelling the part which each germ-layer takes in the 

 formation of each tissue and organ. 



His generalisation that two of the germ-layers give rise 

 exclusively or almost exclusively to one kind of tissue 

 excited great interest at the time, ,and gave the direction 

 to histogenetic research for quite a number of years, though 

 in the end it turned out to be insufficiently founded. 



Though Remak's germ-layer theory had thus principally 

 a histological orientation, it laid down the main lines of the 

 modern morphological treatment of the germ-layers. 



