DESIGN A PROMINENT FACTOR IN NATURE 365 



animals, man included. All are the outcome of a common design. The universe is to be regarded as a harmonious 

 whole. It is in no sense a patchwork. The inanimate physical part of it supplies the original bodies of plants and 

 animals : it also provides a home and food for them. The inanimate and animate kingdoms cannot be separated 

 from each other even for the shortest interval of time. The two are interdependent in the widest sense. Not only 

 are plants and animals indebted to the physical universe for everything they contain at the outset, they are also 

 indebted to it for subsistence throughout their entire lives. The heat, the moisture, the atmosphere, and the 

 pabulum of plants are all physical. Plants form the food of animals, so that even the food of animals is physical 

 at one remove. Heat, moisture, air, and food are necessary to both plants and animals, and both are constantly 

 taking in nutritive materials and giving out waste products. Plants and animals are active and passive by turns : 

 they require rest at stated intervals. Again, the physical universe comes to the rescue : the seasons, and day and 

 night, are provided. Plants and animals, as a rule, rest more or less completely during the night : they also rest 

 in a wider sense during winter. Eest in plants and animals does not mean a complete cessation of the activities 

 of hfe, but only a damping or lowering down. A large number of plants partially close their leaves at night— in 

 other words, sleep. The same is true of animals. Both plants and animals are more active in summer than in 

 winter, and not a few hibernate. 



The juices of plants and animals circulate with less vigour during the night than during the day, and during 

 the winter than during the summer, but the juices are never suppressed or their movements wholly stopped. The 

 juices and movements are both present, and they are slowed and quickened to meet the vicissitudes of the seasons 

 and the alternations of day and night. All this means that the relations which exist between the inorganic dead 

 kingdom and the organic living one are of the most fundamental and intimate description. Cell growth is only 

 possible at certain temperatures, and is prevented by excess of cold or excess of heat. Proofs of design in the 

 inorganic and organic kingdoms, and of the adaptation of the one to the other, everywhere abound. Not only do 

 plants and animals directly proceed from the physical universe, but all their modes of hfe and habits conform to 

 it. Nay more, their movements (when movements occur) are adapted to it. Here again design and law and order 

 come to the front. The physical universe provides three great highways for animals, namely, the earth, the water, 

 and the air, and all animals which elect to traverse these highways must have their travelling organs and surfaces 

 modified and adapted to one or other. To this there is no exception. The land animals which walk and run must 

 be provided with small feet ; the swimming animals with tails, fins, and flippers ; and the flying animals (insects, 

 birds, and bats) with wings. The travelling organs of animals furnish a striking proof of design. They are specially 

 modified to meet the requirements of the earth, water, and air respectively ; the earth providing an unyielding 

 fulcrum for the feet of animals, the water a yielding incompressible fulcrum for the tails, fins, and flippers of fishes 

 and sea mammals, and the air a still more yielding and highly compressible fulcrum for the wings of insects, birds, 

 and bats. 



Wings, of all the travelUng organs, are the most delicately and beautifully constructed. They are marvels of 

 design, being at once strong and light, accurately poised, and mobile and elastic in an astonishing degree. They 

 are of three kinds, as seen in the insect, bird, and bat (Plates U., liii., and liv.). In every case they are triangular 

 in shape, slightly twisted upon themselves, and delicately and exquisitely graduated ; the thicker parts occurring 

 at the root and along the anterior margin, the thinner and most elastic parts at the tip and along the posterior 

 margin. So inexorable is the law which regulates the make and shape of wings, that some of the winged seeds — 

 those of the plane tree, for example — conform to the prevaiUng type. The winged fruit of the plane tree might, as 

 far as the structure and shape of its wings are concerned, be mistaken for a large moth. 



The wing of the insect is a very dream as regards structure, function, and colour. The dainty, deUcate, ever- 

 varying tints of the wing of the butterfly ; the transcendently beautiful tracery of the wing of the dragon-fly ; and 

 the extraordinarily complicated yet simple movements of all wings, baffle description. It is only the entomologist, 

 physiologist, and physicist who can even approximately appreciate their many perfections. 



It would be easy to multiply indefmitely examples of design in the organs of locomotion as a whole, but as this 

 subject is treated at considerable length in another part of the work, it is not necessary to discuss it further 

 at present. 



The lesson to be learned from the foregoing (and it is an important one) is that the needs of plants and animals 

 as regards food, and the modes and means by which they obtain it, exercise a marked influence on their general 

 form and that of their organs, and must be taken into account in considering types and all kinds of classification. 



The simplest plants and animals (cell plants and animals, protista, amoebae, &c.) have ew wants, and there 

 is next to no need for differentiation ; although even in these their bodies are not formed of absolutely homogeneous 

 materials. A little plain food suffices. As soon, however, as the food becomes compound, varied, scarce, or difficult 

 to procure, distinct organs become a necessity. An ahmentary canal or its equivalent, which means a digesting 



