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Trāchēā′rian, pertaining to the tracheate arachnidans; Tra′chēāry, pertaining to the trachea; Trā′chēāte, -d, having a trachea.—ns.

Arachnida, a-rak′ni-da, n.pl. a sub-class of Tracheate Arthropoda, embracing spiders, scorpions, mites, &c., first separated by Lamarck from the Insecta of Linn�us.—adj.

No tracheate Crustacea are known, but some terrestrial Isopoda develop pulmonary in-sinkings of the integument.

The Tracheae.—In regard to tracheae the very natural tendency of zoologists has been until lately to consider them as having once developed and once only, and therefore to hold that a group “Tracheata” should be recognized, including all tracheate Arthropods.

We are driven by the conclusions arrived at as to the derivation of the Arachnida from branchiate ancestors, independently of the other tracheate Arthropods, to formulate the conclusion that tracheae have been independently developed in the Arachnidan class.