ANATOMY AND PHYSIOLOGY. 75 
communication. Experiments on the perception of 
sound are singularly open to such objections, and I 
will not build on any conclusions from them. The 
proof from comparative anatomy, and from the fact 
that an instrument shaped in the form of the wasp’s 
antennse is a very good means of collecting and 
conveying sound to the point where it can be appre- 
ciated, seems to me the best proof we are likely to 
get that the antenne of wasps are really their ears. 
The various forms which the corona, the little 
yellow patch which lies between the origin of the 
antenne, presents have been already fully described 
in pointing out the distinctions between the several 
species. The external figure of the clypeus is less 
varied. This is the broad yellow shield on which 
wasps wear the characteristic devices of the different 
species. It is of an elliptic form above, with occa- 
sionally a notch in the middle line. As the sides 
diverge they come into contact with the lower limb 
of the compound eyes. The outline is completed 
below by two straight lines converging to a point, 
more or less truncated in different species, corre- 
sponding to the commissure of the mandibles. The 
clypeus gives form and width to the face, and pro-. 
tects the soft parts of the mouth which lie imme- 
diately behind and beneath it. 
The structure of the mouth has been made the 
basis of one system of classification of insects. But, 
as these parts are not as open to common observation 
as the wings, the system of Fabricius has been super- 
seded by that of Linnzeus, which supplies much more 
