184 FOUKTH REPORT — 1834. 



different groups, but considered their value as furnishing cha- 

 racters for distinguishing species. He seems to think, that in 

 general, if not in all cases, they are available for this purpose, 

 and advises that selection be made of those which are placed on 

 the middle of the sides of the body, and near the lateral line, not 

 only as being the largest, but as those in which the form is most 

 constant in a given species. M. Kuntzmann has instituted se- 

 veral divisions or classes amongst scales, in which they are ar- 

 ranged according to their form and structure. It would, how- 

 ever, occupy too much I'oom to follow him in this part of his 

 subject. Before quitting this class, I may just allude to two 

 papers by Dr. Hancock, in the London Quarterly Journal of 

 Science for 1830*, in which he has made some remarks on the 

 composition of the fin rays in fishes. Dr. Hancock has dwelt 

 much upon the importance of the character derived from the 

 number of these rays, which he considers as oflPering the best 

 diagnostic marks for the discrimination of species. This cha- 

 racter, however, must be employed \^ith some limitation, since 

 it will be found much more variable in some groups than others. 



IT. AxNULOSA, Cuv. 

 Cuvier, in his B^gne Animal, places this division below that 

 of the Mollusca, which last he appears to have regarded as 

 standing higher in the scale of organization on account of its 

 circulatory system. Geoffroy, gxiided by his peculiar views re- 

 specting the vertebral structure of the Annulosa, to which allu- 

 sion has been already made, has disputed the propriety of this 

 arrangement t, and considers that the Mollusca shoidd decidedly 

 give precedence. It is obvious, however, that these two groups 

 are formed upon such entirely different plans, that they scarcely 

 admit of direct coiiiparison in this respect. Each has its own 

 peculiar marks of affinity with the higher animals ; and it is only 

 by supposing two points of departure from the Vertehrata, and 

 arranging the Invertehrata in a double series, that we shall pre- 

 sent a system at aU conformable with nature. This double route, 

 indeed, was long since pointed out by Lamarck J, and subse- 

 quently by Latreille§, MacLeayll, and Blainville^. Latreille has 

 reconsidered the subject in his latest work, the Cours cV En- 

 tomologie, published in 1831. He there supposes** the In- 



• pp. 136, 287. 



t See his Cours dc I' Flist. Nat. des Mammif., Lecons 2 & 3. 

 X Hist. Nat. des An. sans Vert., torn. i. p. 457. 



§ 111 a memoir published in 1820 under the title of Passage des Animaux 

 Inoertelres aux Vertebres. 8vo. 



II Horte Entom. p. 206, and elsewhere. 



1J Principes d'Anat. Comp , tab. 2. •* p. 15. 



