SKETCH TABLES OF GENERA. 
Reliable dichotomous tables of genera are of great help as giving a short cut to 
the identification of species ; but such tables must be used with caution, for it is 
impossible, within small limits, to do more than direct study into certain lines, 
founded on characters which, after all, may not prove to be natural. Linnseus 
modestly met the objections made to his classifications that they were not natural, 
“ that he was willing to adopt such a natural system, when it was found, and that 
it would be preferable to his own artificial system ” ; which in the instance of botany 
was based on the sexes of plants. His words in extenuation of his own incomplete¬ 
ness of knowledge in natural things, I may be allowed to quote, as addressed to 
Dr. Haller, of Gottingen, in 1737 : “If you detect any mistakes of mine, I rely on 
your superior knowledge to excuse them ; for who has ever avoided error in the 
wide and extended field of nature? ... I am still a learner, not learned.”* 
The following tables are constructed primarily on the forms of the pronotum 
(which in the Centrotidae are thought to be distinctive), and secondarily on the 
character of the suprahumeral processes. The neuration of the wings is not here 
considered, as it appears to be too vague from its variability, though Stal and also 
Dr. Goding have studied the characters. My figures have been drawn simply as 
they appear under the miscroscope, and without the trammels of any hypothesis to 
modify them. 
* Sir J. E. Smith’s “Correspondence of Linnseus,” vol. ii. p. 234 et seq. 
