REPORT ON ZOOLOGY. 149 



tei'ual Characters of the four Classes of Cnistaced, BIyriupoda, 

 Araclmida^ and Insecta, with the Orders and other Subdivisions 

 of the three first of these Classes." In the same year he com- 

 menced the Zoological Miscellany, which, though principally- 

 intended for the illustration of new or little known species, con- 

 tains (the 3rd vol. especially, published in 1817,) an indication 

 of many new groups in different classes of zoology, with their 

 characters and natural affinities. In 1 8 15, he published the article 

 Entomology in the Edinburgh Encyclopccdia-, and in the same 

 year he commenced th.e Malacostraca Podophthalma Britannice, 

 which tended so much to our further knowledge of the Crustacea. 

 Besides the above. Dr. Leach also wrote the articles Annxjlosa 

 andCiRRiPEDES in the Supplement to the jEncyclop{edia£rita7i- 

 nica, the latter containing an entirely new classification of these 

 animals. It is much to be regretted, that soon afterwards the la- 

 bours of this distinguished naturalist were interrupted by illness. 

 He had prepared and nearly completed a valuable work on the 

 British Molhisca, to the natural arrangement of which group he 

 had devoted great attention. Part of it was printed, though 

 never published. His other works, however, sufficiently testify 

 the obligations conferred by him on zoologj^ At the same time 

 they form a marked epoch in the history of this science, as con- 

 nected with our own country. Since the time of their publica- 

 tion many other excellent naturalists have arisen amongst us to 

 contribute to its advancement, to whom I need make no further 

 allusion at present, as of some I shall find occasion to speak 

 hereafter. 



II. Of the primary Types of Form, and other leading Divisions, 

 in the Animal Kingdom. 



Cuvier considered the animal kingdom as exhibiting four pri- 

 mary types of form, to which he gave the names of Vertebrata, 

 Mollusca, Annulosa, and Radiata. The leading characters are 

 derived from the nervous system, which Virey was the first to point 

 out* as the most important part of their organization, and there- 

 fore the most fit to be selected as the groundwork of the system. 

 Cuvier's first enunciation of this arrangement was in a memoir 

 published in the 19th vol. of the Ann. du Mus. in 1812, being five 

 years before the appearance of the R^gne Animal. In it he ob- 

 serves, that he regards these four types or general plans as those 

 after which all animals appear to have been modelled, and of 

 which the subordinate divisions are only comparatively slight mo- 

 difications, founded on the development or addition of certain 

 parts, which produce no essential change in the original plan, 

 * Nouv. Diet, d'llist. Nat., Art. Animal. 



