Ixvi Journal of Comparative Neurology, 



property of irritability. Simple protoplasm, then, — and much more, 

 nervous protoplasm — has the property of returning a motor response to 

 a sensory stimulus ; this is mechanical, or, at least, it is not truly voli- 

 tional. This motor discharge is the result of the chemical or biological 

 instability of the protoplasm and at first will follow lines of least resist- 

 ance. The strength of the reaction will depend, in a measure, at least, 

 on the strength of the stimulus, and the reaction against all stimuli will 

 at first be spasmodic, i. e. non-adaptive, just as the reaction against a 

 too powerful stimulus is today in the highest animal. These primitive 

 reactions, however, at once come under the influence of the law of 

 natural selection and for normal intensities of stimulus the non-adaptive 

 reactions will speedily be eliminated in accordance with known evolu- 

 tionary principles. Of course, this view of the origin of reflexes (and 

 of instincts, as well) has not yet been proven to the satisfaction of all ; 

 and yet, since it is held by a respectable number of biologists, it ought 

 not to be neglected in a discussion of this sort. 



Let us now examine in the hght of this theory the illustrations 

 brought forward by Mr. Romanes, which he states were chosen because 

 they are fairly typical of the phenomena of reflex action in general. 

 First, as to the reflex withdrawal of the foot upon an irritation, he says, 

 " Even in its present fully formed condition it is fairly questionable 

 whether it is of any adaptive vah/e at all. The movement performed 

 is no doubt an adaptive movetneni ; but is there any occasion upon 

 which the reflex mechanism concerned therein can ever have been of 

 adaptive use ? Until a man's legs have been paralyzed as to their vol- 

 untary motion, he will always promptly withdraw his feet from any in- 

 jurious source of irritation by means of his conscious intelligence. 

 True, the reflex mechanism secures an almost inappreciable saving in 

 the time of the response to a stimulus, as compared with the time re- 

 quired for response by an act of will ; but the difference is so exceed- 

 ingly small, that we can hardly suppose the saving of it in this partic- 

 ular case to be a matter of any adaptive — much less selective — impor- 

 tance." Again, we are referred to the familiar complex of actions ex- 

 hibited by the brainless frog. Of these actions those associated with 

 the maintenance of equilibrium are selected for especial consideration. 



Both of these cases are regarded as clear cases of lapsed intelli- 

 gence and as quite inexplicable by any application of the theory of 

 natural selection ; but we have seen that this conclusion will not be uni- 

 versally accepted. Furthermore, in his first case, the slight saving of 

 time by the reflex response as compared with the volitional response is 

 by no means to be neglected. I should regard it as an adaptive char- 



