EXTERNAL ANATOMY OF INSECTS. 401 
ably. But in the Coleoptera, and many other Orders, 
the colours of the skin are mixed in its horny tissue, 
nearly as those of the Testacea are in their calcareous 
shells*. In the perfect insects, therefore, in most cases, 
we may consider the ep¢dermis and rete mucosum as to- 
gether forming the exterior and coloured integument of 
insects—that part which in the table, since it is not pro- 
perly an epidermis, I have distinguished by the name of 
Lixoderma. 
The learned author just quoted has observed nothing 
under the skin of white- blooded animals that he regards 
as analogous to nervous papille®. In some parts of in- 
sects, as in the lamellee of the antennz of the Petalo- 
cera, and the extremities of the joints, especially the last, 
of many palpi, there is however an appearance of them; 
and it seems reasonable to suppose that where the sense 
of touch resides, there must, even in insects, be some- 
thing of a papillary tissue. 
With regard to the innermost integument of the ver- 
tebrate animals,—the /eather, or real skin,—this learned 
comparative anatomist finds nothing analogous to it in 
the integuments of insects‘; but as he does not notice 
it, he appears to have overlooked the substance that lines 
the outer crust, or evoderma, in the Coleoptera and most 
other Orders. This is not always easily detected; but it 
may generally be discovered by breaking, or rather tear- 
ing (not cutting), after having cleared away the muscles, 
any part of the body of an insect. It is always very vi- 
sible on the under side of elytra 4, but is not discoverable 
* Anat. Compar. ii. 553, b Ibid. 5572 ° Tbid. 560. 
4 Prate XXVIII. Fie. 2. .a!. 
VOL. III. 2n 
