140 Zoological Society. 



members of the animal kingdom up to their own position in the 

 scale, on the other hand (so that, for instance, man passes through 

 forms resembling, but not identical with, those of many animals from 

 the lowest monad up to his own position in the scale), are inexpli- 

 cable on the theory that the forms of animals are regulated by final 

 causes only ; but are in perfect accordance with that other which 

 holds that there is expressed in the structure of animals some abstract 

 idea, which running through all the frame, and modified to all pur- 

 poses of need, and manifested in all variety of conditions, is yet one 

 and the same. 



It must be admitted that the force of these arguments may, to 

 some extent, be barred by an assertion which it is difficult fully to 

 answer, viz. that our ignorance of final causes is so great as to allow 

 us no room to argue on the existence of other causes from their ap- 

 parent inadequacy ; nevertheless as the other supposition seems to 

 have in it no improbability, but as I think the contrary, it may be 

 admitted as at least what best suits our present knowledge. 



The belief in the existence of other laws of organization besides 

 that of final causes does in no wise lessen or obscure the argument of 

 natural religion derived from it, which was advanced with great per- 

 tinency by the ancient Stoical philosophers, and has been amphfied 

 by Derham, Paley and others in our own country. 



I now proceed to the second portion of my paper. 



Section II. 



There are reasons derived from the structure of animals below 

 the Vertebrata which might induce us to expect that the vertebrate 

 skeleton should be composed of elements of a common character. 



1 . So soon as the nervous system assumes the form of a line or 

 chain down the body of the animal, the whole structure puts on a 

 segmental or annular arrangement. Thus in the Annelida the body 

 consists of numerous segments, similar one to the other, with the 

 exception of the anterior one or head, which is sometimes slightly 

 different in form, but in other instances only distinguishable by the 

 presence of a mouth. Each segment has its proper nervous gangUon, 

 connected by two fibrous commissures with those of the neighbouring 

 division. 



2. But these segments are subject to change. Thus the Poly- 

 desmidce, a family of the Myriapoda, exhibit the posterior part of 

 the body composed of segments similar to those above described, 

 whilst in the anterior part each segment is the result of the coales- 

 cence of two original ones. In the Chilipoda, the same process has 

 gone on further ; so that all the apparent segments are thus com- 

 posed by the anchylosis of two original ones at an early period of 

 growth, as proved by the two pair of legs which each one bears, and 

 the double nervous ganglia which they contain, the nervous centres 

 of the original elements ha\dng approximated to one another without 

 coalescence (Newport on Myriapoda, Phil. Trans. 1843). 



3. But not only does the progression from lower to higher forms 

 in the scale of the animal kingdom teach us how segments of the 



