270 THE AMERICAN NATURALIST. [VoL. XXXIV. 
tionable, since pronounced variations often occur within the 
limits of a single group. 
Until a closer relationship can be dion in the lines of de- 
scent 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 ap- 
pendage is a result brought 
about by certain indefinite 
factors, and that in these 
groups it does not neces- 
' sarily imply a phylogenetic 
relationship. 
That the trochanter of the 
Myriopoda and Hexapoda 
X6 represents a distinct seg- 
Wie. jiis raris Moewhewi ment doeme obvious, and 
coxa; x, area formed by development of coxal that its fusion with the 
groove [Fig. 4 ig and corresponding to lateral 
portion of c, Fig femur took place in some 
ancestral A tbe form appears probable. 
Three sclerites, as a rule, enter into the composition of the 
segment to which the name coxa is given, vís., coxa genuina, 
meron, and trochantin. Audouin? applied the name “ trochan- 
tin"? to the lateral margin of the posterior coxa (meron) in 
Dytiscus circumflexus, erroneously believing it homologous with 
the trochantin on the anterior and mesal coxa of Buprestis 
1 Compare Arachnida, or, in Coleoptera, the metathoracic coxa of Dytiscus and 
Hydrophilus 
s Recherches anatomiques sur le thorax des animaux sien et celui des 
insectes hexapodes en particulier. Ann. Sci. Wat., tome i, p. 12 24. 
3 This word had been previously used by Chaussier [Littré, Dio. de Médecine, 
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 transferring 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 (H 
philus, certain Cerambycidz, etc.). 
