8 THE SHORTER SCIENTIFIC PAPERS 



is absent in the Crustacea. Homologies based upon the 

 form of the segment and manner of articulation certainly 

 appear questionable, since pronounced variations often 

 occur within the limits of a single group. ^ 



Until a closer relationship can be shown in the lines of 

 descent of the two groups, Hexapoda and Crustacea, it 

 would seem that an attempt to homologize the segments 

 of the appendages would scarcely be justified. For the 

 time being, we must assume that the segmentation of an 

 appendage is a result brought about by certain indefinite 

 factors, and that in these groups it does not necessarily 

 imply a phylogenetic relationship. 



That the trochanter of the Myriopoda and Hexapoda 

 represents a distinct segment seems obvious, and that its 

 fusion with the femur took place in some ancestral 

 myriopod-like form appears probable. 



Three sclerites, as a rule, enter into the composition of 

 the segment to which the name coxa is given, viz., coxa 

 gemiina, meron, and trochantin. Audouin^ applied the 

 name "trochantin"^ to the lateral margin of the posterior 

 coxa (meron) in Dytiscus circumflexus, erroneously 

 believing it homologous with the trochantin on the 

 anterior and mesal coxx'^ of Buprestis gigas, which he 

 subsequently mentions.^ Later, in his contribution to 

 Cuvier's "Le Regne Animal," he figures the prothoracic 

 trochantin of Oryctes nasicornis. The present confused 

 terminology of these segments is due to the preceding 

 error of Audouin. Newport^ made a somewhat similar 

 error by describing the anterior margin of the coxa {coxa 



^Compare Arachnida, or, in Coleoptera, the metathoracic coxa of Dytiscus and 

 Hydrophilus. 



^Recherches anatomiques sur le thorax des animaux articules et celui des insectes 

 hexapodes en particulier. Ann. Sci. Nat., tome i, p. 125, 1824. 



This word had been previously used by Chaussier [Littre, Diet, de Medecim, 

 p. 1632] during the latter part of the eighteenth century to designate a small process 

 on the upper part of the femur in the human skeleton. From the note Audouin 

 appends, he evidently felt some constraint in conforming to the custom of transfer- 

 ring such terms to invertebrate anatomy when no homologies could be demonstrated. 



*In the metathorax of the Coleoptera the trochantin has been lost through 

 specialization, although traces of it are noticeable among many forms (Hydrophilus, 

 certain Cerambycidi, etc.). 



Etude de la poitrine ou des pattes inferieures et laterales du mesothorax. Ann. 

 Sci. Nat., tome i, p. 426, 1824. This is merely a continuation of Recherches 

 anatomiques. 



^Todd's Cyclopedia of Anatomy and Physiology, p. 916, 1835-59. 



