J 24 DESIGN IN NATURE 



species are known— one of which (M. electricus) is met with on the Nile. They grow to four feet or thereby. 1 had 

 an opportunity of studying some fine specimens of the electric fish of the Nile at the Gezireh Aquarium Cairo 

 (1904-5) and on one occasion, very many years ago, I received, at Edinburgh University, an electric shock trom 

 an electric fish from Old Calabar. It sufficed to excite the Calabar specimen slightly, and to put one s hand into 

 the water in which it was swimming, whereupon one or more very distinct shocks would be felt, and, once telt, 



could never be forgotten. .^ i. i. i. j„ oil r^^roT tha 



In the electric sheath-fish, the electric organ is not confined to one particular part, but extends all over the 

 body beinc. most developed in the abdomen. It is contained between two aponeurotic membranes beneath the 

 skin and is composed of rhomboidal cells which contain a gelatinous substance of rather firm consistence The 

 nerve distributed to the organ forms an outstanding feature of the arrangement It has its ongin ^-^^^^^f^^^ 

 has no connection with nerve ganglia, and consists of a single enormously developed nerve trunk. In this i differs 

 materially from the arrangement met with in the electric eel, where more than 200 separate nerves are distnbuted 



to the electric organ. , . > r ^ ■ i a • t+ „++„;„„ +^ 



The greatest of the electric fishes is the electric eel {Gymnotus electricus) of tropical America. It attains to 

 as much as six feet in length, and, according to the famous traveller, Humboldt, is dangerous to man and beast. 

 It occurs in great plenty in Brazil and the Guayanas. 



The astounding feature in the electric organs of the gymnotus is their enormous nerve supply. More than 

 200 nerves are distributed to the organs, and the nerves are very much larger than the sensory and motor nerves 

 going to other parts of the body. As the electrical organs are special, so, in a large measure, are the nerves distri- 

 buted to them The nerve supply consists of continuations of the anterior branches of the spinal nerves. They 

 furnish branches not only to the electric organs but also to the skin and muscles of the back of the gymnotus. _ 



The electric organs take the form of two pairs of longitudinal bodies ; the one pair situated between the skm 

 and muscles on the back of the tail, the other pair between the skin and muscles along the anal fin. They have an 

 involved and intricate structure, consisting as they do of a numerous series of perpendicular and transverse septa, m 

 the interstices of which are imbedded prismatic cells containing a gelatinous substance. The septa are separated 

 from each other by about the thirtieth of an inch, measure an inch in length, and contain some 240 cells, which secure 

 for the electric organs a simply enormous surface. 



It is difiicult to reahse how intimately related the electric organs of fishes are to those of ordinary electric 

 batteries, and how certain fiving creatures should have been provided with an apparatus for manufacturing, storing, 

 and discharging electricity, giving them a power over their victims, or mayhap enemies, not possessed by even 

 man himself. 



The electric organs of fishes can only be regarded as special creations, as the sense organs are. It is incon- 

 ceivable that they could have been evolved from any living structure in the remote past, or that they could have 

 been produced by natural selection, into which the elements of chance and utihty enter. The electric organs are 

 massive and heavy, and, while they are eminently serviceable, when fully developed, to the electric fishes possessing 

 them, no fish or series of fishes throughout the ages could have been burdened by them while undergoing a slow 

 process of evolution, and while they were totally unfit for work of any kind. Mr. Darwin was wholly unable to 

 explain their existence, and keenly felt the strain they put on his theory of " natural selection." Indeed he is 

 said to have experienced a cold shiver whenever confronted with what, to him, was an insuperable difficulty. 



§ 30. Lines of Communication and Force, Nervous and Otherwise. 



Every one who has studied vital manifestations must have been struck with the fact that in plants and 

 animals — the simplest as well as the most complex — there are means of communication as between their several parts 

 and particles, and as between each individual organism and the physical universe. In other words, there is a means 

 of communication between the atoms and molecules of the cells and tissues of plants and animals on the one hand, 

 and between the individuals themselves and their surroundings or environment on the other. 



The lines of communication in the lowest plants and animals are by no means well defined. Thus in the cell 

 plants and animals — the yeast plant and amoeba, for example — where there is little differentiation, and where there 

 is, so to speak, a common structure and a common function, every part of the individual seems capable of transmitting 

 impulses either from within or from without. In these cases, the living mass is endowed with a power which 

 enables it to grow, divide, reproduce itself, and move. Every part reacts upon every other part, and all are under 

 the influence of life and vital and physical force. Every part of the individual displays a low form of sensitiveness 

 or its equivalent, and this in turn involves a rudimentary form of cognition and consciousness. The sensitiveness 

 connects the several parts of the individual with each other, and the individual as a whole with its surroundings. 



