TRANSACTIONS OF SECTION D. DEPT. OF ZOOLOGY AND BOTANY. 367 



An animal is an organism all the actions of which are necessarily determined 

 by the adjustments of its various organs, and hy its environment. But even its 

 sensations cannot be regarded as mere accompaniments of its activities, but as 

 guides and directing agencies intervening in the circle of its actions, and as facts, 

 in the chain of physical causation. The sight of a stick may change the course of 

 actions which a dog would otherwise have pursued — that is, the feeling of the 

 moment, together with the faint recurrence of various past feelings and emotions 

 therewith associated which the sight of the stick calls up, may cause such change. 

 Besides its feelings, the general and the organic movements of the doo- are like 

 our own, governed by a multitude of organic influences which are not° felt, but 

 which operate through the nervous system, and so must be taken as parallel with 

 those which are felt, i.e. as unfelt, nervous psychoses. The animal then, like 



each of us, is a creature of activities partly physical, partly psychical, the latter 



both the felt and the unfelt — being directive and controlling. 



As we descend to the lowest animals, the evidence as to sentience fades. Yet 

 from the resemblances of the lowest animals and plants, and from the similarity of 

 the vegetative functions in all living creatures, we may, I think, analogically conclude 

 that activities also take place in plants which are parallel with, and analogous to 

 the unfelt psychoses of animals. As Asa Gray has said with respect to their 

 movements: 'Although these are incited by physical agents (just as analogous 

 kinds of movements are in animals), and cannot be the result of anything "like 

 volition, yet nearly all of them are inexplicable on mechanical principles. Some of 

 them at least are spontaneous motions of the plant or organism itself, due to some 

 inherent power which is merely put in action by light, attraction, or other external 

 influences.' 



I have already adverted to insectivorous plants, such as Dioncea. In such 

 plants we have susceptibilities strangely like those of animals. An impression 

 is made, and appropriate resulting actions ensue. Moreover, these actions 

 do not take place without the occurrence of electrical changes similar to 

 those which occur in muscular contraction. Hardly less noteworthy are the 

 curious methods by which the roots of some plants seek moisture as if by instinct 

 or thoseby which the tendrils of certain climbers seek and find appropriate support' 

 and having found it, cling to it by a pseudo-voluntary clasping, or, finally, those 

 by which the little ' Mother-of-a-thousand ' explores surfaces for appropriate hollows 

 in which to deposit her progeny. 



Nevertheless, nothing in the shape of vegetable nervous or muscular tissue has 

 been detected, and as structure and function necessarily vary together, it is impossible 

 to attribute sensations, sense-perceptions, instincts, or voluntary motions to plants 

 though the principle of individuation in each acts as in the unfelt psychoses of 

 animals and harmonises its various life processes. 



The conception then which commended itself to the clear and certainly 

 unbiassed. Greek intellect of more than 2,000 years ago, that there are three 

 orders of internal organic forces, or principles of individuation, namely, the rational 

 the animal, and the vegetal, 1 appears to me to be justified by the light of the 

 science of our own day. 



1 Difficult as it confessedly is to draw the dividing line between animals and 

 plants, such difficulty is not inconsistent with the existence of a really profound 

 difference between the two groups. That there should be a radical distinction of 

 nature between two organisms, which distinction our senses, nevertheless more or 

 less, fail to distinguish, is a fact which on any view must be admitted, since animals 

 of very different natures may be indistinguishable by us in the germ, and in the earlier 

 stages of their development. The truth of this is practically supported by the late Mr 

 Lewes, who says (as to the difference between the protoplasms from which animals' 

 and plants respectively arise) : ' That critical differences must exist is proved by the 

 divergence of the products. The vegetable cell is not the animal cell ; and although 

 both plants and animals have albumen, fibrine and caseine, the derivatives of these are 

 unlike. Horny substance, connective tissue, nerve tissue, chitine, biliverdine . 

 and a variety of other products of evolution or of waste, never appear in plant's ■ 

 while the hydrocarbons abundant in plants are, with two or three exceptions' 



