Note 65 — 1. Family BALANIDÆ, (or Sessile Cirripedes). (continued 2)

Zenker, in his ‘Physiological Remarks on the Daphnidæ,’ (‘Journal of the Microscopical Society,’ 1853, p. 274), speaks of a “tripartite azygous eye” as common amongst Crustacea, and as occurring “in conjunction with the aggregated eyes in Artemia, Argulus, &c.; but as appearing regularly in all the Branchiopoda and Siphonostomata as the earliest visual organ.” Hence I conclude that this azygous eye is the homologue of that single eye which appears in the earliest larval stage of Cirripedes; and that the compound eyes of the cirripedial pupa, answer to the aggregated eyes of Artemia and Argulus, &c., with the difference, that in these latter genera the single eye is retained. See, also, Von Siebold, ‘Anatomie Comparée,’ tom. i, p. 435.