160 THE PHILOSOPHY OF BIOLOGY 



consciousness arise ? We cannot even imagine its 

 association in a functional sense with, the train of 

 events forming an afferent impulse. In some form or 

 other mechanism must assume a dualism — a parallelism 

 of physical and psychical processes. Physical events 

 in the central nervous system are associated with 

 psychical ones — when the former occur so do the latter 

 — yet the former are not "causes " in any physical sense 

 of the latter. Consciousness follows cerebral energy- 

 transformations as a parallel " epiphenomenon." At 

 once we leave the province of mechanism, and how can 

 we remain content with such a limitation of our descrip- 

 tions ? And if we conclude, as we seem obliged to do, 

 that consciousness is an affective agency in modifying 

 our responses to external stimuli, does not this in itself 

 show that our concept of behaviour as a purely physico- 

 chemical process is insufficient in its exclusiveness ? 



We return to a consideration of the main results 

 of experimental embryology in a later chapter, but let 

 us notice here what is the direction in which these 

 results, and those of the analysis of instinctive and 

 intelligent action, carry us. It is towards the con- 

 clusion that physico-chemical processes in the organism 

 are only the means whereby the latter develops, and 

 grows, and functions, and acts. In the analysis of 

 these processes we see nothing but the reactions studied 

 in physical chemistry ; but whenever we consider the 

 organism as a whole we seem to see a co-ordination, 

 or a control or a direction of these physico-chemical 

 processes. Nageli has said that in the development 

 of the embryo every cell acts as it if knew what every 

 other cell were doing. There is a kind of autonomy 

 in the developing embryo, or regenerating organism, 

 such that the normal, typical form and structure comes 

 into existence even when unforeseen interference with 



