150 Mr. W. S. MacLeay on the Anatomy of the 



to the organs they denote, and are compatible moreover with what ought 

 to be our grand object in anatomy, namely, legitimate generalization (and 

 not fanciful comparisons with the human subject), I shall of course have 

 pleasure in adopting them. In some few cases indeed our venerable 

 countryman's nomenclature may be preferred for purposes of concise de- 

 scription to that of M. Audouin, although for the philosophical view of 

 the subject M. Audouin's terms can scarcely with safety be altered, and 

 have moreover the universally acknowledged right of priority. Thus, if 

 I may be permitted by such naturalists as most properly insist on the 

 right of those who give the first name, I would in the description of spe- 

 cies prefer the use of Mr. Kirby's terms prosternum, mesosternum and 

 metasternum ; although to give a proper understanding of the compara- 

 tive anatomy of insects, I would for the same parts use M. Audouin's 

 otherwise less convenient terms sternum of the prothorax, sternum of the 

 mesothorax, and sternum of the metathorax. The nature and object of 

 the present paper, however, preclude me from saying more on the subject 

 of the " Introduction to Entomology" ; this work being evidently, by its 

 laying so much stress on differences, rather suited to some artificial system 

 than to the study of the natural one, which depends on generalization. I 

 shall therefore commence the present review of the Theory of Compara- 

 tive Anatomy in Insects by repeating that M. Audouin's Researches have 

 so far the right of priority, and above all of philosophical criticism, as to 

 justify me in pursuing the path he has pointed out. I am not, however, 

 disposed to be a servile follower, and where I differ from him I shall have 

 no hesitation whatever in pointing out the reasons for my dissent. 



It will be recollected by the readers of the " Horce EntomologiccE^^ that I 

 was inclined in that work to adopt the theory that every annulose animal * 

 has a tendency to be decapod, or more properly to have five pairs of tho- 

 racic appendages answering to the five thoracic segments. I also assigned 

 my reasons for believing that although the typical number of segments in 

 the body of an annulose animal might be fifteen, yet that the most general 

 number of segments in the body ought to be considered as thirteen, the 

 number in caterpillars and other larvse : and I ventured to hint that all 

 winged insects, I might have said all Annulosa, may be resolved into this 



* This theory, however, is only partially correct. 



