INTERNAL ANATOMY OF INSECTS. 77 
tance which nature has attached to the oxygenation of 
the germ while in the matrix. And judging from ana- 
logy, we may infer that the access of this element is as 
carefully secured after the egg is laid, as before. The 
eggs of most insects being of a porous texture, often at- 
tached to the leaves of plants, and some of them embed- 
ded in the very substance of a leaf or twig a , are in a 
situation for the abundant absorption of oxygen : and 
the pouch of silk in which the eggs of spiders and Hy- 
drophili are deposited, may probably, from Count Rum- 
ford's experiments, be of utility in the same point of view. 
In the case of the TricJioptera and other insects b whose 
eggs are dropped into the water enveloped in a mass of 
jelly, this substance perhaps serves for aerating the in- 
cluded embryo, in the same way with the jelly surround- 
ing the eggs of the frog, dog-fish, &c. It would be 
desirable to ascertain whether the former jelly be of the 
same nature as the experiments of Mr. Brande have 
shown the latter to be c . It is not improbable that the 
singular rays that terminate the eggs of Ne-pa d may in 
some way be connected with the aeration of the egg. 
To what I have before remarked with regard to the 
vital heat of insects e , I may under this head very pro- 
perly add a few further observations. I there stated, that 
the temperature of these animals is usually that of the me- 
dium they inhabit, but that bees, and perhaps other gre- 
garious ones, furnish an exception to this rule f . A con- 
firmation of this remark is afforded by Inch, a German 
a Vol. I. p. 446—. III. p. 70. b Ibid. G8— . 
c Phihs. Trans. 1820. 218. d Vor.. III. p. 94, 
e Vol. II. p. 228-. f Ibid. p. 211. 
