DUGES 87 



of the Arthropod skeleton, though he admitted that 

 in Arthropods the dorsal surface was turned towards 

 the ground, basing this assumption on the position 

 of the nervous system, and also, curiously enough, 

 on the inverted position of the embryo on the lower 

 surface of the yolk. He considered that the mandibles 

 and first maxillae of Arthropods were the homologues 

 of the upper and lower jaws of Vertebrates, adducing 

 as confirmatory evidence the fact that in snakes the 

 rami are separate. The labium was the equivalent of 

 the hyoid, the labial palps and maxillipedes the equiva- 

 lent of the " hyoid " elements which form the branchial 

 arches. 



But Duges' main contribution to morphological method 

 was his conception of the living organism as a colony of 

 lesser units, which were themselves real " organisms." " By 

 organism the author means a complex of organs which taken 

 together suffice to constitute, ideally or actually, a complete 

 animal. An ' organism ' is, as it were, an elementary or simple 

 animal ; several organisms combined form a complex 

 animal" (p. 255). Duges hit upon this principle, which was 

 first suggested to him by A. Moquin-Tandon's work on the 

 leech (1827), as a great aid in demonstrating the unity of 

 plan and composition throughout the animal kingdom. 1 

 According to his view there are three main types of animals 

 (i) Biserials, including bilaterally symmetrical animals, 

 composed of two parallel series of "organisms" ; (2) Radiates, 

 composed of "organisms" arranged like the spokes of a 

 wheel ; and (3) Raceme-animals, in which the separate 

 " organisms " were disposed more or less irregularly, in 

 bunches (p. 257). The unitary "organism" is supposed to 

 be the same in all, only the arrangement differing. Duges 

 of course admitted that the centralisation of the com- 

 plete organism became greater the higher it stood in 

 the scale, and that this held good also in individual 

 development. The appendages of Articulates and Verte- 

 brates were thought of as the members of as many 

 separate organisms. He went so far as to suggest that the 



1 His views were more fully elaborated in his Mcmoire sur la 

 conformite organique dans I'cchelle animale, Montpellier, 1832. 



G 



