470 Mr. N. A. Vicors on the Natural Affinities 
the Tenuirostres and Fissirostres, which for the most part confine 
themselves to one species of food, whether animal or vegetable. 
While the Scansores and Dentirostres, holding an intermediate 
station between the extremes, are intermediate also in the extent 
of their food ; fruit and berries being added to the animal food of 
the rest in some families, and in those more particularly which 
are contiguous to the omnivorous typical tribes. 
The foregoing figure affords, moreover, an opportunity of ob- 
serving some striking analogies between different groups in the 
order. It has been remarked by the author of the ** Hore Ento- 
mologice," who was the first to exhibit the relations of nature in a 
similar geometrical figure, and thus almost to reduce the science 
of natural history to geometrical precision, that, in figures con- 
structed as the above, representing a series of circles united 
by affinities, the external groups of one circle always bear an 
analogy to the corresponding groups of those which are conti- 
guous*. This analogous connexion serves to point out the 
causes of many important coincidences among the different 
groups of the Insessores. It explains the reason why the Picide 
on the one hand, and the Trochilide and Cinnyride on the other, 
families otherwise totally differing in their food and habits, should 
yet resemble each other in the common use to which they apply 
the tongue. It explains why the Trochilus, the Hirundo, and 
the Caprimulgus should- be assimilated in the feebleness and 
almost uselessness of the bill; that of the former being but a 
sheath to defend the tongue, that of the latter but a secondary 
fence to prevent the escape of the prey. It accounts for the cha- 
racters of the genus Hirundo being so far transferred to the La- 
* See Hore Entomologice, p. 396, where the meaning of an external group is ex- 
plained. In the foregoing diagram the Picide, Cinnyride; Trochilide, Hirundinide, 
Caprimulgide, Laniade, Merulide, Sturnide, Corvide, and Psittacide, are the exter- 
nal families. They comprise, in fact, the typical groups of each tribe. 
niade 
