TWO PATHS, ONE GOAL. 



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development of a nervous system, found in an animal. The 

 greater number of animal adaptations is in proportion to their 

 higher s(;ale of being. Again, the three elementary groups 

 of structures subserving Eelation, Nutrit/ion, and Ileproduction 

 suffice to group simply the bulk of adaptations found in tlie 

 animal world. Here, again, most of the evidence is too familiar 

 to need more than a brief reference, and so familiar also as to 

 make one commonly omit to observe the vast potential evidence 

 for purpose comprised in any individual and well-known animal. 

 We may allude to — first, the bones, muscles, skin, hairs, feathers, 

 scales, spines, claws, teeth, horns, any single group of which 

 would afford material for a short treatise ; second, the nutritive 

 functions of animals necessarily require much more complicated 

 contrivances and structures to carry them out than the simpler 

 processes sufficient for plants. Between the absorption of 

 nutritive matter by a protozoon through its ectosarc from its 

 watery surroundings ana the digestive apparatus of man, we have 

 to take a mental journey which is indeed immense. Thus the 

 whole ascending series of animal forms shows so simple an 

 arrangement as that of the sponges, and so complicated a group 

 of mechanisms as the fourfold stomach of a ruminant. But in 

 addition to the absorption and comminution of nutriment in 

 the mouth, gullet, stomach, and intestine, there are such impor- 

 tant structures in all degrees of development as salivary glands, 

 liver, spleen, pancreas, and kidneys, their perfection rising with 

 the general ascent of the individual form, organs for excretion 

 and assimilation being in some cases put to work of both kinds. 

 But nutrition in the proper sense of the word includes the 

 process of obtaining the required amount of oxygen from air 

 or water for the due maintenance of the purity of the blood, 

 and this brings in the wondrous groups of mechanisms by 

 which, for example, the insect will absorb gases from the air 

 through its trachea, the fishes from the water through gills, 

 the amphibia by gills at one period and lungs at another period 

 of their lives, the mammal by a varied and ascending scale 

 of respiratory arrangements culminating in those of man. 

 Third, the methods by which the propagation and perpetuation 

 of the species in animals is secured are not less varied or 

 wonderful than those to which allusion has been made. The 

 former were primarily for the benefit of the individual, these 

 ai-e for the benefit of the succeeding race. They include the 

 gemmation and fission of the protozoon and the myriads 

 of forms of reproductive apparatus intervening between such 

 primitive contrivances and those of the higher mammals. To 



