Some writers are of opinion that there are only two thoracic spiracles in Insects, considering the third as belonging really to the abdomen. Looking on the point as at present chiefly one of nomenclature, we make use of the more usual mode of expression.
As on last page, and also op. cit. v. 1868, p. 278.
Bull. Ent. Ital. xii. 1880, p. 46.
It may be worth while to repeat that "joint" means a piece, and is the equivalent of "link" in a chain.
Materials for the Study of Variation, 1894, p. 413.