366 DESIGN IN NATURE 



apparatus in some form, is called for, and this implies a circulatory and respiratory apparatus to distribute and 

 purify the nutritious juices. Nor does the matter rest here. The food may not be at hand, and may have to be 

 searched for and even caught. TravelUng and capturing organs in the shape of protrusions of sarcode, pseudopodia, 

 cilia, flagella, teeth, limbs, fins, flippers, wings, &c., become imperative. These travelling and capturing organs in 

 turn necessitate (or may necessitate) the presence of bones, muscles, nerves, brain, and other structures capable of 

 producing movements. 



The question of food very largely dominates the shape and the degree of differentiation of plants and animals. 

 From the first they are modified to cope with the food on which they are to subsist. Indeed it may safely be 

 asserted that plants and animals are primarily modelled and planned to meet the food requirements. The call 

 for food is incessant, and much time and energy are necessarily devoted to securing and dealing with it. The appetite 

 for food, and the fimdamental tendency to reproduction, account for the major portion of the activities of both 

 plants and animals. 



Living organisms as a whole, and all parts thereof, must, in the nature of things, possess the power to sustain 

 and reproduce themselves ; and in order to discharge these two primary functions they are, in all cases, specially 

 designed and specially constructed. The desire for food takes precedence of that for reproduction, as plants and 

 animals must be well fed and healthy before reproduction can take place. Not only the general shapes of plants 

 and animals, but the shapes of their several organs, and the arrangement of the atoms and molecules forming the 

 organs, are all modified to deal effectively with the subject of food. Plants and animals in the matter of food are 

 aggressive. They lay themselves out for and stretch forth their substance to obtain it. They advance towards the 

 food and are ready to seize it when it is in their vicinity. The food has to be drawn into their substance. The 

 craving for food is peculiar to plants and animals and is in themselves. Food does not produce appetite or act as a 

 stimulus, neither is it to be regarded as an irritant. Hunger in animals occurs equally in the absence and presence 

 of food. The several kinds of food, moreover, have nothing to do with the production of the organs provided to 

 seize and deal with it. These are supplied independently and in advance. Bach plant and each animal has its 

 special food and other endowments. 



In the insectivorous plants, Venus's fly-trap, sundew, &c., the leaves are flattened and furnished with highly 

 sensitive hairs, which when touched inaugurate movements capable of catching flies, beetles, ants, &c. In the collared 

 monad (a low animal form) a pear-shaped body surmounted by a funnel-shaped cavity with a vibratile flagellum is 

 supplied. This flagellum, wielded with extraordinary dexterity and skill, produces water currents which float the food 

 into the interior of the animal. In the paramecium the body is covered with a multitude of swiftly-moving ciha 

 which enable it to dart in any direction it pleases in pursuit of food. In the vorticella the cilia invest the margin 

 of the cup-shaped disc, and by their movements direct the floating particles of food unerringly into its substance. 

 In addition the vorticella is provided with a most exquisite spiral stem, by the aid of which it can instantly project 

 itself against or recede from submerged particles, edible or otherwise. Other animals adopt other modes and assume 

 various shapes in securing food. The Articulata become segmented and develop legs, by means of which they move 

 towards their food. These movements may be slow, as in the caterpillar, or comparatively quick, as in the spider 

 and ant. As we rise in the scale of being, distance and time become elements in the food supply. The larger, 

 complex animals require more food, and in order to obtain it must travel further afield and at a greater pace. 

 Travelling extremities, fins, flippers, and wings must be added to the food-securing apparatus. We have, as a con- 

 sequence, not only creeping things, of which the caterpillar is a good example, but creatures which can walk, run, 

 and leap on the land ; fishes and water-going mammals which can swim in the water ; and insects, birds, and bats 

 which can fly in the air. A series of the most extraordinary modifications is introduced by the food requirements. 

 The food question practically determines the anatomy and physiology of plants and animals. 



It is scarcely possible to attach too much importance to the food-securing and procreative powers. The food 

 supply, physically speaking, is at the root of the whole matter. Plants and animals, as explained, derive their sub- 

 stance, directly or indirectly, from the inorganic kingdom : plants also derive their food from the same source and 

 at first hand ; animals deriving their food at second hand from the plant, or at third hand from other animals. The 

 special forms, arrangements, and laws pecuhar to the inorganic kingdom become, by incorporation, the forms, 

 arrangements, and laws of the organic Idngdom. These laws are practically inexorable, and so it happens that the 

 elements, and the atoms composing them, both without and within living bodies, have a tendency to act in given 

 directions and to assume characteristic typical shapes. In this we have an explanation of the radiating, concentric, 

 curvilinear, spiral, dendritic, branching, and other arrangements met with in crystals, plants, and animals respectively! 



The reproductive function, as stated, is second in importance to the food-securing and digesting, assimilating 

 function : but here again all the pecuharities referred to reappear. Plants and animals resemble each other, and 

 both resemble certain crystals ; but plants and animals in the reproductive process simply ring the changes, as' each 



