In Organized Beings. 97 



group any individual belongs. I might refer to the cliaracters 

 of the mollusca, so strongly marked in the cirrhopode-;, although 

 the latter group unquestionably belongs to the articulated se- 

 ries ; or to the characters of the bat and bird, so strikingly dis- 

 played in the pterodactylus. Without wishing to enter into 

 the discussion of the circular and quinarian theories, I may 

 state my conviction that Messrs Macleay, Fries and Swainson, 

 are perfectly correct in maintaining, that the types of each 

 group are definitely separated from one another ; but that their 

 aberrant members (where the chain is complete) have the 

 strongest relations of affinity. Every one must perceive that 

 the extended researches which are at present being cari'ied on, 

 both in zoology and botany (and these not confined to the ex- 

 isting epoch, but extending to past ages) are every day contri- 

 buting to fill up the links that before seemed deficient ; and it 

 is now generally regarded as the true character of a complete 

 natural group, that it passes by almost imperceptible grada- 

 tions into every adjoining one. To take the example of the 

 cephalopodes and fishes. Although the former are universally 

 regarded as the most developed of the mollusca, no conchologist 

 would assume the class as the type which most prominently 

 represented the pecuhar characters of that division of the ani- 

 mal kingdom. In like manner, fishes, which are the least de- 

 veloped of the vertebrata, are far from being typical of their 

 division. We might expect, therefore, on the principles just 

 laid down, that the hiatus should not be very wide between these 

 two classes ; and although Cuvier was of opinion, that an im- 

 passable gulf separates the vertebrata and invertebrata, more 

 extended research has shown, that though there may be little 

 general resemblance in form between any fish and any cepha- 

 lopod, yet there is a very gradual transition in the structure of 

 most of the systems of these two classes. Thus the nervous 

 system, and internal skeleton of the highest cephalopodes, may 

 almost be placed on a level with those of the lowest cartilaginous 

 fishes ; the arrangement of their circulating apparatus is strik- 

 ingly intermediate between that of the mollusca in general and 

 that of fishes ; and whilst, in their organs of locomotion, we see 

 a beautiful adumbration of those which are characteristic of 

 fishes, so, in many fishes we may trace the remains of those 

 . ^•0. XLV. — JLLV 1837. G 



