86 Till: FOLLOWERS OF (iKOlTUOY 



relative to one another. Many of the names which he 

 proposed are still in use; it was he who introduced the 

 terms prothorax, mesothorax, and metathorax, for the three 

 segments of the insect's thorax. He used Geoffrey's 

 Lot de balanccinait to explain cases of correlative 

 development, such as the relation between the size of the 

 front wings and the development of the mesothorax. In 

 another paper Audouin compared the three pieces of the 

 dorsal skeleton of Trilobites to the tergum and the upper 

 part of the " flanc." l In a third paper of about the same 

 time he tried to establish the homologies of the segments 

 throughout the Articulate series with less success than 



o 



Savigny. 



Later on, in conjunction with Milne-Edwards, he demon- 

 strated the unity of composition of the nervous system in 

 Crustacea, showing how the concentrated system of the crab 

 was formed by the same series of ganglia as in the Macrura. 



The entomologist Latreille also tackled the problem of 

 the homologies of the segments in the different classes of 

 Arthropods (Cuvier, loc. cit., p. cclxxii.). He thought he could 

 find fifteen segments in all Arthropods. He made the 

 retrograde step of likening the head of insects to a single 

 segment. But some of his homologies showed morphological 

 insight, e.g., his comparison of the " first jaws " of Arachnids to 

 antennas, because they were placed above the upper lip. It 

 was he who first pointed out the resemblance of the leaf-like 

 gills of Ephemerid larva; to wings, and suggested that wings 

 were " a sort of tracheal feet." 



He made also a rather hazy and speculative contribution 

 on Okcnian lines to the problem of the relation of Arthropods, 

 to Vertebrates, likening the carapace of Crustacea to an 

 enormously developed hyoid, the appendages of the tail to 

 the ventral and anal fins of fish. The masticatory organs of 

 Arthropods were jaws disjointed at their symphysis ; antenna-, 

 nostrils turned outside in. 



Duges also made a comparison of Articulates with 

 Vertebrates.- He did not accept Geoffrey's \\-rtebral theory 



1 Cuvicr, M, : in. Ac<ui. Set'., iv., p. cclxx., 1824. 



- Ac<id. Sci. 1 8th Oct. 1831. Extract in Ann. Sci. Nat., xxiv., pp. 

 254-60, 1831. 



