482 THE GENERAL PRINCIPLES OF ZOOLOGY 



and a few living, microscopic cells ; if placed under the proper 

 conditions these cells, in the course of three weeks, will have 

 increased in number, absorbed the lifeless matter about them 

 and shaped themselves into tissues and organs, nerves, bones, 

 muscles, etc. ; we may say that the cells know how to do this, 

 but we do not mean that they possess intelligence in the sense 

 that man possesses it any more than we should ascribe intelli- 

 gence to the minute particles of quartz, which select other 

 particles of the same nature and unite with them until they have 

 built up the perfect quartz crystal. 



Passing from the simple reactions of single cells as in the 

 Protozoa to the simple coordinated actions of groups of cells as 

 in the sea anemone, we may take as the next step in the evolu- 

 tion of animal behavior, the simple reflex action ; this involves 

 a much higher degree of anatomical differentiation. In this 

 process there is required a sensory organ, an afferent nerve 

 which shall transmit the stimulus from the sensory surface to a 

 nerve center, and an efferent nerve to transmit the impulse 

 from the nerve center to the organ which responds. The 

 process thus becomes of considerable complexity, and we 

 scarcely know enough about animal behavior in its details to 

 determine how it may have arisen from the simple direct 

 responses of the lowest animals. It is distinctively an involuntary 

 process, and yet, in its more complex manifestations, may exhibit 

 purposive phenomena. Thus if we take a recently decapitated 

 frog and put a drop of acid on the thigh, the foot will be drawn 

 up and attempt to rub the acid off ; if the foot be held so that it 

 cannot move, the foot of the other leg will attempt to remove the 

 acid ; yet the decapitated frog if left to itself exhibits no volun- 

 tary movements, and without spontaneous movements we cannot 

 attribute intelligence to the organism ; can we go a step further 

 and say that consciousness is likewise absent from the reflex 

 action? Effective consciousness certainly is absent, — it is pre- 

 cluded by the involuntary nature of the phenomenon ; on the 

 other hand, we can conceive of a momentary consciousness present 

 during the activity of the nerve center, not effective to alter the 

 response, — a simple accompaniment of the reflex act, — called 

 into existence by the stimulus and immediately disappearing. 

 Taking such a rudimentary type of consciousness as a starting- 



