16 DEFINITION OF THE TERM INSECT. 
kind and degree of sense and intelligence that they pos- 
sess, seems rather fanciful than founded in nature, since 
many insects show a greater portion of them than many 
vertebrate animals. Compare in this respect a dee with 
a tortoise*. Lamarck divides his group of animaux sen- 
sibles into two sections, namely, Articulated animals, ex- 
hibiting segments or articulations in all or some of their 
parts; and Inarticulated animals, exhibiting neither seg- 
ments nor articulations in any of their parts. Insecta, 
Arachnida, and Crustacea, belong to the first of these 
sections, which he defines as “those whose body is di- 
vided into segments, and which are furnished with jointed 
legs bent at the articulations.” Insecta he defines— 
“ Articulate animals, undergoing various metamorphoses, 
or acquiring new kinds of parts—having, in their perfect 
state, six feet, two antenne, two compound eyes, and a 
corneous skin. The majority acquiring wings. Respira- 
tion by spiracles (stigmates), and two vascular opposite 
chords, divided by plexus, and constituting aeriferous tra- 
chee, which extend every where. A small brain at the 
anterior extremity of a longitudinal knotty marrow, with 
nerves. No system of circulation, no conglomerate glands. 
Generation oviparous : two distinct sexes. A single sex- 
ual union in the whole course of lifec.’ ARACcHNIDA he 
defines— Oviparous animals, having at all times jointed 
legs, undergoing no metamorphosis, and never acquiring 
new kinds of parts. Respiration tracheal or branchial : 
the openings for the entrance of the air spiraculiform 
(stigmatiformes). A heart and circulation beginning in 
* See on this point MacLeay, Hor. Entomolog. 209—. 
® Anim. sans Vertebr. iii, 243. ° bid. iii. 245. 
