INTERNAL ANATOMY OF INSECTS. 23 
manufacturer also in Paris, fed 800 spiders in an apart- 
ment, which became so tame that whenever he entered 
it, which he usually did bringing a dish filled with flies 
but not always, they immediately came down to him to 
receive their food?. 
All these circumstances having their due consideration 
and weight, it seems, I think, most probable, that as 
insects have their communication with the external world 
by means of certain organs in connexion with their ner- 
vous system, and appear to have some degree of intellect, 
memory, and free will, all of which in the higher animals 
are functions of a cerebral system, and at the same time 
in other respects manifest those which are peculiar to 
the sympathetic system,—it is most probable, I say, as was 
above hinted, that in their system both are united. 
I must bespeak your attention to a circumstance con- 
nected with the subject of this letter, which merits parti- 
cular consideration: I mean the gradual change that 
takes place in the nervous system when insects undergo 
their metamorphoses; so that, except in the Orthoptera, 
Hemiptera, and Neuroptera Orders, in which no change 
is undergone, the number of ganglions of the spinal chord 
is less in the imago than in the larva. ‘There seems an 
exception indeed to this rule in the case of the rhinoceros- 
beetle (Oryctes nasicornis), in the larva of which there is 
only one ganglion, while in the imago there are four®. 
But as this one ganglion occupies the whole spinal mar- 
row, it is really of greater extent than the four of the 
imago; so that even in this case there is a concentration 
a N. Dict. d’ Hist. Nat. ii. 279—. 
» Cuv. Anat. Comp. ii. 319, 337. 
