30 THE AMERICAN NATURALIST. [VoL. XXXVI. 
We are inclined, however, to return to the old view ; for we 
find that in many insects each compound eye is situated in the 
axis of an annular sclerite, which may be the basal segment of 
the ocular appendage. Certainly if the eyes were merely spe- 
cialized portions of the lateral sclerites, we should not expect: 
them to be surrounded by a ring-like 
suture, which in some cases is com- 
paratively remote from the specialized 
portion of the body-wall that forms the 
eye. 
These sclerites bearing the compound 
eyes may be termed ¢he ocular sclerites; 
they are represented in Fig. 18, os. 
Passing to the second segment, we 
uM find at the base of each antenna an 
. 1%. — Head of a cricket, annular sclerite (Fig. 18, as), which is 
T mM EM linc iu comparatively few insects and 
which has not been described. It is 
most clearly shown in the Plecoptera (Fig. 19, as). This we 
believe represents the lateral field of the antennal segment, 
7.£., the lateral element of the sternite and what is left of the 
pleural element of the segment, which is greatly reduced. This 
sclerite may be termed she antennal sclerite. 
The position of the antennal sclerites should be discussed. 
If the clypeus represents the median field of the sternite of 
the antennal segment, as we believe, the primitive position of 
the antennal sclerites was laterad of the clypeus, and we should 



Fic 
expect to find the rudiments of them in this position, t.e., lat- 
erad of the procephalon, in the early stages of the embryo. 
Many observers, however, have described the antenna as aris- 
ing in a postoral position ; how can this be explained? A 
study of the figures given by these authors! shows that while 
a line connecting the two antennz would pass in some cases 
behind the mouth, it is by no means so clear that the basal 
part of the rudiment of the antennal sclerite does not abut 
against the procephalon. In fact, the very figures given to 
~ ? Weismann, '63, Fig. 22; Graber, '88; Figs. 1 and 2; Heider, '89, Fig. 102 
a (Fig. 7 above); Patten, '88 (Fig. 10 above). | oe 

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