UNITY OF SYSTEM. 73 



this final state of the inferior creature is far more perfect and complete in 

 its functions than the transition state of the superior creature, so that the 

 latter while progressive, may be said to be a degradation of the former 

 when fully developed, being but a means or passage to a higher state, 

 which the inferior creature cannot only never attain to, but from which 

 it recedes more and more as it advances towards its final state or perfection. 

 The earlier and generally hidden state of the superior creature may thus 

 be studied in the ultimate state of the inferior creature, the former cor- 

 responding to the latter, though in an imperfect and undeveloped form. 



The independent existence, and more or less distinct and peculiar form 

 of the earlier creature, is a character of the Amphibia amongst the Yer- 

 tebrata, and of the Articulata generally; and these in their early stage 

 represent the perfect state of other classes which are inferior to them. It 

 is also an invariable rule that the transition state of the Articulata or 

 higher class is degraded or imperfect in comparison to the permanent state 

 of the lower class. Thus it appears that the weakness and imperfection of 

 the early state of a creature is necessary for its advancement to a higher 

 state, in conformity with the law of degradation; its early state being 

 inferior to the final state of an inferior creature, and its final state superior 

 to the early state of a superior creature. 



The law being thus manifest in the comparison of one kind of creature 

 with another kind, it remains to be shewn how it appears in the compar- 

 ative organization of every creature, that is, in the comparison of one part 

 of its structure with another part. In the process of growth the decrease 

 or degradation of one part is simultaneous with the growth of another; 

 the substance which was assimilated to and enlarged one part of the structure 

 being partly transferred to another of superior faculties; and when this 

 process is very conspicuous, as in most of the Articulata, the creature is 

 said to undergo a metamorphose. The lower members by being degraded 

 are thus partly taken up or assimilated to higher members. During the 

 above process there is a period of weakness, or infirmity, or helplessness, 

 which all creatures more or less undergo previous to their increase in size 

 and strength, or before they pass to a higher degree of organization or of 

 existence. It may be clearly seen how this transitory incapacity or sus- 

 pension of the faculties corresponds to the times of cessation of existence 

 between the epochs before mentioned. 



Parts of the animal structure which are primary, and have their full 

 development, and occupy nearly the whole of the organization of the lower 

 classes, are successively more and more degraded in the higher classes, 

 and become more and more partial, superficial, and unimportant. In a 

 worm every segment of the body seems to be equally developed. In one 

 of the Myriapoda, the head has its peculiar organs, but all the other 



