126 DESIGN IN NATURE 



of origin of the individual or with a centre developed during the process of differentiation. The ovum is the centre 

 of the developing foetus — the brain is the centre or terminal of the adult vertebrate animal. 



While the shape of the plant and animal is determined to a large extent by the hues of communication and 

 force, the latter in turn are dominated within Umits by the former. Thus, in rod-Uke plants and animals the lines 

 of communication and the direction of force are in straight lines ; in globular plants and animals with a central 

 origin they are in straight lines and in curves, whereas in spiral plants and animals they are helical. 



In plants and in the lowest animals there is no trace of a nervous system as we know it, but a nervous system 

 or its equivalent may nevertheless exist in both in an undifferentiated form. The fact that some of the lowest 

 animals — the amoeba for instance, and certain of the higher plants, such as the sundew — can, and do, move in given 

 directions, at certain times, and to definite ends, goes far to prove not only that there are lines of communication 

 akin to nerve tracts, but that there are also controlhng forces which move along these Hues, resembling in many 

 respects nerve forces. 



To trace the rise and progress of the nervous system in animals to its culmination in man is one of the most 

 difficult problems in physiology. Animals which were long supposed to be devoid of a nervous system (the jelly- 

 fish for example) are now known to possess it. The nerves in the jelly-fish are not only extremely delicate, but they 

 are also very soft. The condition of fluidity or softness is characteristic even of the human brain, which is the 

 highest representative of nerve substance. The brain, which transcends all other organs in power, is, strange to say, 

 nine-tenths water. A Uttle excess of softness in the nervous system of the jelly-fish would make the nerves so 

 transparent as to be invisible. It follows from this that a fluid or semi-fluid nervous system in animals, and even in 

 plants, is well within the possibihties. Certainly the movements and simultaneous power of feehng possessed by 

 certain plants, and the majority of even the lowest animals, plainly indicate some such arrangements. 



If any one takes the trouble to study under the microscope the countless myriads of animalcules and low animal 

 and vegetable forms which swarm in water and Uquid generally, and if, in particular, he watches how in their 

 darting about in search of food they regulate their speed, the direction in which they move, and, in especial, how 

 they avoid colliding with each other, he will be forced to admit that none of the movements he observes are chance 

 movements. If this be conceded, then the obvious corollary is that the movements referred to are voluntary. Volun- 

 tary movements, however, as we know them, imply a nervous system, or its equivalent, and this in turn necessitates 

 sensitiveness of a kind. Sensitiveness implies feeling, and feehng cognition, which culminates in the consciousness 

 of the higher animals. The most complex structures are, at their beginnings, developed from comparatively simple 

 and very slightly differentiated protoplasm. In plants and the lowest animals, if nerve substance exists, it must 

 occur in a fluid or semi-fluid, transparent state. The semi-liquid condition of nerve matter in the jelly-fish favours 

 this view. Living things are not chance products. They are, on the contrary, distinct entities. From the lowest 

 to the highest they have independent roles to perform, and they perform them with remarkable regularity and 

 uniformity. In order to do so, they must be provided with bodies in the form of living matter, and these bodies 

 must be amenable to control as regards the intake and output of food, as regards respiration, circulation, sensation, 

 movement, excretion, &c. ; but control imphes directly or indirectly the possession of a nervous system, or its 

 equivalent in an undifferentiated or invisible form. This argument is valid as regards the entire race of animals. 

 It also apphes, within limits, to quite a large number of plants. 



Founding as we do our ideas of sensation, perception, movement, &c., on a brain, sensory and motor nerves, 

 muscles, &c., as we find them in the higher animals, we are apt to deny to the lower and lowest animals, even in 

 a rudimentary form, the structures and attributes which we find in a greater or lesser degree of perfection in the 

 higher and highest animals. Nothing could be more unphilosophical. Brain and nerve substance and muscle as 

 mere hving matter, have not necessarily any advantage over other living matter, and there can scarcely be a 

 doubt that in all living matter, even in protoplasm, there are the potentialities and powers which lend themselves 

 to the formation at once of the simplest and most complex plant and animal organisms. These organisms, the 

 simplest equally with the most complex, are independent beings, capable of managing their o^vn affairs, each in its 

 own way. If the most complex exercise their functions through the instrumentahty of a brain, nervous svstem and 

 muscles, that is no reason why the more simple should not exercise similar functions by other means and methods 

 or by similar means and methods in what appears to us (with our hmited powers of observation) an undifferentiated 

 form. To take an example. The vacuoles in certain water plants exhibit rhythmic movements in every respect 

 similar to those displayed by the mammalian heart ; the vacuoles closing suddenly and opening slowly, as in the 

 several' compartments of the heart. But plants have neither muscles nor nerves in the ordinary sense. Again 

 the heart of the chick, while yet a mass of nucleated cells, and before it even contains blood, displays characteristic 

 rhythmic movements. Here again the muscles and nerves to which we attribute the rhythmic movements of the 

 adult heart are absent. 



