No 400.] SEGMENTS OF THE HEXAPOD LEG. 273 
meron) into the so-called coxa. Theoretically the episternum 1 
and epimeron may be regarded as corresponding basal seg- 
ments of these fused pieces, and taking into consideration the 
apparent absence of a piece homologous with the meron in the 
Diplopoda, we are led to the interesting inference that this 
group represents a class in which each primitive metamere 
bears a pair of appendages, while the Chilopoda and Hexapoda 
represent a widely divergent class, in which two primitive 
metameres have attained a more com- 
plete fusion, the rudimentary append- 
age belonging to each posterior segment 
fusing with the base of the functional 
appendage belonging to the anterior 
metamere? The posterior appendage 
would then be represented by the 
meron and epimeron.* In this case 
we can refer the origin of coxa genu- 
tna and episternum, as well as the 
meron and epimeron, to the same 
causes which produce segmentation 
in the appendage. The trochantin 
appears to be nothing more than a 
part of the antecoxal piece, a lateral 
prolongation of which became con- 
stricted off in a primitive form. 
Again we are confronted with the 
question as to the origin of the ap- 
pendages in the Arthropoda, whether they are ventral or dorsal 
parapodia, or a fusion of the two, as in Nereis, or whether the 
ing with meron and epimeron, 
1 Frequently tl to be cut off from the coxa by the sternum 
or by the trochantin, buth in esis cases the coxa is usually prolonged internally, so 
that it west the epistern 
nt there dry to be better evidence for believing that these pieces 
Ph a fusion of the segments than to hold that an exopodite and entopodite 
are represented. 
8 A study of the position and homologies of certain of the pleural and dorsal 
sclerites in Hexapoda and Chilopoda appears to confirm this inference. 
* While thus far the Petty of embryological evidence appears to be against 
this view, it seems possible that secondary modifications have caused a misinter- 
pretation of the lines of cidem 
