DEFINITION OF THE TERM INSECT. ws 
many. The majority couple often in the course of life*.” 
I shall next add his definition of Crustacea: “ Ovi= 
parous, articulated, apterous animals, with a crustaccous | 
integument more or less solid, having jointed legs ; eyes 
either pedunculate or sessile, and most commonly four an- 
tenne, with a mazilliferous mouth seldom rostriform ; 
maxille in many pairs placed one over the other ; scarcely 
any under-lip ; no spiraculiform openings for respiration ; 
Jive or seven pair of legs; a longitudinal knotty marrow 
terminated anteriorly by a small brain. A heart and ves- 
sels for circulation. Respiration branchial with external 
branchie, sometimes hid under the sides of the shell of the 
thorax, or shut in prominent parts ; sometimes uncovered, 
and in general adhering to particular legs or éo the tail. 
Each sex usually double®.” 
I have given Lamarck’s definitions of these three 
classes, all considered as Insecta by Linné, that by com- 
paring them together you may be better enabled to ap- 
preciate the system of this author. On looking over the 
characters of the Arachnida as here given, you will see 
-at once that it consists of heterogeneous animals—for in 
fact he includes in this class not only the Trachean 
Arachnida of Latreille, but the Ametabolia of Dr. Leach, 
or the Hexapod Aptera, and the Myriapoda. 
I shall next copy for you Latreille’s definitions of Zn= 
secta and Arachnida from his latest works. 
“Insecra: A single dorsal vessel representing the 
heart : two trunks of trachee running the whole length 
of the body, and opening externally by numerous spi- 
racles; two antenne ; very often upper appendages for 
Jught, indicating the metamorphosis to which the animal 
* Anim. sans Vertebr. iii. 245. b Tbid. 
VOL. III. Cc 
