MEMOIR OF LATREILLE. 31 
being of insects, is still merely artificial, that it is not 
sufficiently strict, for the order of the Suctoria is an 
apterous group, not in its right place among the 
Insecta Pterodicera. And also the groups which 
are here considered as equivalent to the Tetracera, 
Myriapoda^ Apterodicera^ and Pterodicera^ are by no 
means of equal value, but the two first and two last 
are most closely allied ; the former are the subordi- 
nate members of a higher group, and the latter also 
could at most be placed as equivalent to the orders 
of the Insix'ta pterodicera." 
Before leaving this subject, it may be desirable to 
show briefly, in juxta-position with the above, some 
of the various changes our author afterwards made in 
his arrangement, for in every successive work im- 
portant alterations were effected. In his ""' Coutside- 
rations generales sur I'Ordre Xaturel des Animaux 
composant les Classes des Crustaces, des Arachnides, 
et des Insectes," * the Linnean Insecta was divided 
into three equivalent groups, Crustacea, Arachnides 
(including the Insecta aptera of the former system), 
and Insecta. Such was likewise the arrangement 
which appeared in Cuvier's Regne Animal t, but 
the groups were differently defined, and some of the 
contents ot each transferred to another. There was 
likewise the necessary addition of the order Strep- 
siptera, recently discovered by Kirby. After seve- 
ral other changes, of more or less importance, in 
different works, we come to that embodvincj his 
latest views, published in his '' Cours d'Entoino- 
logie,":}: which was completed only a short time before 
* Paris, 1 810, 8v(x t i'aris, 1817. :;: Paris, 1832. 8vo. 
