REPORT ON ZOOLOGY. 



227 



The classification of the Cirripeda was greatly advanced by 

 the labours of Dr. Leach, who made a particular study of this 

 class, and instituted several new genera in it. His arrangement 

 is founded upon characters derived from the shelly covering of 

 these animals, which he submitted to a more minute and rigor- 

 ous analysis than any previous observer had done before him *. 



Mr. Gray has also attended to this subject. In the Ann. of 

 Phil, for 1825 f, he has published a synopsis of the genera 

 arranged in natural families. 



IV. Radiata, Cuv. 



As we descend the scale of organization we find the groups 

 defined with less and less certainty. In the present division, 

 our knowledge of their exact limits, we may even say of the 

 number of primary types of form which this division comprises, 

 is so imperfect, that it would be to little purpose to detail all 

 the different arrangements which have been proposed for these 

 animals, the classification of which is probably still destined to 

 undergo great and important revolutions. After all, it is doubt- 

 ful whether we must not admit with MacLeay that they form two 

 groups, each of equal value with that of the Vertebrate, Annu- 

 lose, and Molluscous divisions, instead of one only as Cuvier 

 supposes. In this state of uncertainty, I shall merely take 

 Cuvier's classes in the order in which they stand in the B^gne 

 Animal, and under each state some of the principal additions 

 which have been made of late years to our general knowledge of 

 these animals. This will naturally lead to the mention of several 

 impoijtant steps which have been gained towards an improved 

 classification of them. 



The following are the classes into which Cuvier divides the 

 Radiata : Echinodermes, Intestinaux {Entozoa, Rudolp.), 

 AcaUphes, Polypes, and Infusoires. 



1. Echinodermuta. — To our knowledge of this class I am not 

 aware of many important additions that have been made recently. 

 Since the publication of Tiedemann's work on the anatomy of 

 these animals, which gained the prize from the French Institute 

 in 1812, and which served to clear up many points in the details 

 of their organization, no one appears to have studied their struc- 

 ture more deeply than Delle Chiaje. Several memoirs have 

 appeared by this last author J treating of the genera Echimis, 



* See the article Cirripedes in the Sitppl. to the Encycl. Brit. Also Zool. 

 Journ. (1825), vol. ii. p. 208. 



t vol. xxvi. p. 97. 



X Memorie sulla Storia e Notomi^ degli Animali senza Fertebre. 4to, Nap. 

 1823, &c. 



q2 



