AUDOUIN 85 



they may be modified as " false " mandibles and " false " 

 maxillae, really correspond to the second and third maxilli- 

 pedes in Crustacea, and to the second and third pairs of feet in 

 insects. It is interesting to note that he treats Liuinlus as an 

 Arachnid, pointing out that there is as much difference between 

 Apns and Liinulus as between Cancer and PJialanginin. He 

 describes the " gnathobases " in Phalangiuin and Limulus. 

 We may note 'that he had just an inkling of the modern 

 doctrine that all the appendages of Articulates consist of 

 a basal joint bearing an inner and an outer terminal piece, 

 for he observes that the "cirri" of the maxillipedes of 

 Crustacea give the appendage the same bifid appearance as 

 the appendages of the abdomen and the thoracic legs of 

 My sis (p. 50). 



V. Audouin, in his memoir, Recherches anatoniiqncs snr Ic 

 thorax des aninianx articules} applied the principle of the 

 unity of plan and composition to the exoskeleton of insects, 

 Crustaceans, and Arachnids. His guiding ideas were, "(i) 

 that the skeleton of articulated animals is formed of a definite 

 number of pieces, which are either distinct or intimately fused 

 with one another ; (2) that in many cases, some pieces 

 diminish or altogether disappear, while others reach an 

 excessive development ; (3) that the increase of one piece 

 seems to exert on the neighbouring pieces a kind of influence 

 which explains all the differences one finds between the 

 individuals of each order, family and genus " (Sep. copy, 

 p. 1 6). Geoffroy had already stated, without proof, that the 

 parts of the Arthropod's skeleton, however they might 

 change in shape and size, remained faithful to the principle 

 of connections, at least at their points of insertion. 2 Audouin 

 gave the detailed demonstration of this by his accurate and 

 minute determination of the pieces of the arthropod skeleton. 

 He recognised that the body of Arthropods was made up of 

 a series of similar rings, and that even the compact head of 

 insects consisted of fused segments. In each segment 

 Audouin distinguished a fixed number of hard chitinous 

 parts, the dorsal tergum, the ventral sternum, the lateral 

 " flanc " of three pieces, all to be recognised by their positions 



1 Ami. Sci. Nat. (i), i., pp. 97-135, 416-432, 1824. 



2 Jsis, p. 456, 1820 (2). 



