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THE BASAL SEGMENTS OF THE HEXAPOD LEG. 
L. B. WALTON. 
AT the base of each leg in the Hexapoda are a series of seg- 
ments and sclerites which enter into the composition and serve 
as a support of the appendage. These are the trochanter, coxa 
genuina, meron! trochantin, and antecoxal piece. The difficul- 
ties in the way of accounting for the origin of these segments 
and homologizing them in the various orders have caused mor- 
phologists more or less trouble. 
By reason of the fusion which has.taken place between the 
trochanter and femur in the Myriopoda and Hexapoda, many 
writers on insect anatomy hold that the trochanter is merely a 
portion of the femur which has in some manner become con- 
stricted so as to form an apparent but not an actual segment. 
The fusion, however, between the two parts is a specialization 
acquired during the later embryonic stages of development.? 
A similar case of ankylosis is often noticeable between certain 
segments of the appendages in Crustacea.  Bordage? has 
advanced the theory, from observations based on certain Phas- 
mida, that the two segments have become coalesced in the 
Arthropoda as a result of ecdysis. Since the same fusion, 
however, is very pronounced in the Myriopoda, particularly 
among the Diplopoda, where Verhoeff * believes the trochanter 
1 In order to distinguish between these two parts, which havé been confused 
under the name “coxa,” I have called the piece articulating with the trochanter 
coxa genuina, and the posterior lateral part articulating with the epimeron, meron 
(from wig = thigh), since its lateral margin is always found in articulation with 
the epimero 
*The * recited trochanter " of Hymenoptera [Terebrantia] appears to be 
a secondary modification, the lower part [‘‘afophysis,” Ratzeburg] being derived 
from the femur. This is the view held by Sharp, Camé. Nat. Hist., vol. v, p. 520. 
? On the Probable Mode of Formation of the Fusion between the Femur and 
Trochanter in Arthropoda. Comptes Rendus de la Société de Biologie, tome v, No. 
28, pp. 839-842, 1898. Also Ann. and Mag. Nat. Hist., vol. iii, pp. 159-162, 1899. 
* Ein Beitrag zur Kenntniss der Glomeriden.. 1895. _- 
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