branchiæ

from The Century Dictionary.

• Organs subservient to respiration through the medium of water.
• In Arthropoda, as crustaceans, specifically, the externally projecting processes of the body or its limbs, which are supplied with venous blood (which is thus brought into contact with the air dissolved in water), and constitute a special respiratory organ. See cut under Podophthalmia.
• In Vermes, any appendages of the head or body so modified as to act as a respiratory organ; the various processes which protrude or radiate from the head or other region of the body, and have, or are supposed to have, a respiratory function. See cut under Protula.
• In entomology, gill-like appendages on the bodies of certain insect-larvæ and -pupæ which live in the water, as many dragon-flies and gnats.