PRINCIPLES AND METHODS OF PALAEONTOLOGY. 371 



a hundred subdi\isious, and every man charges himself with the satis- 

 faction of one of these subdivisions, hoping* that, in exchange, liis own 

 ninety-nine wants will be satisfied by others. So that, in one sense, a 

 hundred civilized men may be said to be the equivalent of but one sav- 

 age ; while, if, on the other hand, we regard the nature of the i)roducts 

 of civilization, and balance the sum of the work done on each side, the 

 advantage on the side of civilization is infinite. 



It is j)recisely this division of the physiological* labor, the organism, 

 which constitutes the first of the two great kinds of difference between 

 animals. Some Protozoa have no definite aperture for the taking in of 

 food, no muscles, and no limbs. Every part of the body-wall may serve 

 in turn as mouth or locomotive organ. In others there is a month, but 

 no definite alimentary canal, and the contractile locomotive apparatus 

 is limited to one part of the body. In the Ccelenterata the mouth and 

 digestive cavity are permanently appropriated to that ofiice, though not 

 separate from the rest of the cavity of the body. The motor organs are 

 still more definite and serve as organs of prehension and offense. In 

 the Mollusca the digestive cavity is ijermaneut and completely separated 

 from the walls of the body. A blood system is developed to carry the 

 nutritive matter to all parts of the body. Another portion of the organ- 

 ism is converted into muscle, and can do little but contract ; another 

 has nothing to do but to form shell ; another, the nervous system and 

 organs of sense, is charged with the sole duty of putting the different 

 parts of the organism in relation with one another, and Avith the external 

 world. Thus, in the mollusk, each part of the organism is charged with 

 a special function, and, to the same extent, has become dependent on 

 others. The stomach that digests depends on the blood for its own 

 nourishment. The muscle that enables the animal to seize its prey 

 would perish without the aid of the stomach and the blood, and would 

 be ineffectual without the nervous sj^stem which guides it. The mollusk 

 does no more in the long run than the Amccha; it absorbs food, it modi- 

 fies it, and it exhibits irritability, but the manner in which it does all 

 these things is infinitely superior, and enables it to disi)lay powers of 

 which the Amoeba exhibits no trace. 



It is needless to pursue the argument further, or it would be easy to 

 show that the difference between man and the mollusk, as physiological 

 machines, is of the same kind as that between the mollusk and the pro- 

 tozoon ; in short, phystological perfection is in i)roportion to the division 

 of the labor of the whole organism among organs specially adapted to 

 particular offices. 



The other sense in wliich perfection is attributed to living beings is 

 morphological, t The MoUuscaj an a whole, are more perfect than the 

 Ccelenterata^ because they exhibit a greater number of specialized and 

 diversiform parts and organs, quite irrespective of the functions of 

 those parts and organs ; and the vcrtehrata, in their fundamental char- 

 acter, the possession of a true primordial internal skeleton, exhibit a 

 greater complexity of structure than any mollusk, or any annulose 

 animal. 



It of course usually happens that physiological and morphological 

 complexity go hand in hand, but it should be remembered that the con- 

 junction is not a necessary one. The lowest vertebrate animal, for in- 



* PnVsioLOGY. — The science wiiich treats of the forces exerted by liviuj; beings 

 irrespective of their forms ; except so f;vr as these couti'ibute to the exertion of theso 

 forces. 



tMoHPUOLOGY. — The science which treats of the forms ol living beings without re- 

 ifiird to their functions. 



