BBPORT ON ZOOLOGY. 20/ 



searches of many excellent observers. Some of the most im- 

 portant contributions on the subject of their external anatomy 

 have arisen out of an endeavour to trace analogies of structure 

 in the relative conformation of different groups in this class, as 

 well as in that of insects in general compared with the rest of 

 the Annulosa. Savigny was the first to draw the attention of 

 naturalists to inquiries of this nature in two memoirs on the 

 structure of the mouth of the articulated animals, published in 

 1816*. In one he demonstrated that the same parts were to be 

 found, though modified, in this organ as it occurs both in the 

 Mandibiilata and Haustellata, notwithstanding the apparent 

 dissimilarity of its structure in these two groups. In the other 

 he extended his researches, with the view of establishing similar 

 analogies, to the mouth of the Arachnida, Crustacea, and En- 

 tomostraca. The year 1820 was rich in memoirs of a similar 

 nature to those just alluded to. Latreille first published one on 

 the structure of the wings of Insectst, in which he sought to re- 

 fer to some general law of conformation the organs of locomo- 

 tion in this class, as well as in those oi Arachnida and Crustacea. 

 Latreille' s memoir was followed by three from Geoffroy on the 

 Organization of Insects, already referred to in a former part of 

 this Report as containing the first enunciation of his views re- 

 specting the vertebrate structure of Insects and CrustaceaX. 

 The same year two memoirs were brought forwards by Audouin 

 on the same subject. The object of one was to point out ana- 

 logies of structure between the true Insects and the Crustacea 

 and Arachnida, more particularly as regards the head and its 

 appendages, and the relative development of the segments of 

 the trunk§. That of the other was to generalize an extensive 

 series of observations with respect to the various parts which 

 enter into the composition of the thorax in the different orders 

 of Insects II . Latreille also published two other memoirs besides 



• " Theorie des Organes de laBouche des Crustaces et des Insectes," Mim. 

 sur Us An. sans Vert., Part I. 



+ De la Formation des Ailes des Insectes. 8vo. 



X Journ. Comp. du Diet, des Sci. MM., tomes v. and vi. It was in conse- 

 quence of GeofFroy's first memoiron this subject, read to the Academy of Sciences 

 Jan. 3, 1820, that Latreille was induced to write his memoir (before alluded to) 

 entitled Passage des Animaux Invertebres aux Vertebres, which memoir of 

 Latreille was published, together with his former one, De la Formation des Ailes 

 des Insectes, as an Svo pamphlet. 



§ I am ignorant as to where this memoir was published, or whether it was 

 ever published at all. I know it only fronv Cuvier's Report in the Analyse des 

 Travaux. 



II This memoir was subsequently published in the Ann. des Sci. Nat. for 1824, 

 torn. i. pp. 97 and 416. A short analysis of it had appeared previously in the 

 Bull, de la Soc. Phil, (or 1820. 



