IV. Letters received from the naturalists attached to the transit-of-Venus expedition at Rodriguez

Abstract

Letters from the Naturalists attached to [D ee. 17 nasal sac. In D f neither the ethmoidal nor the trabecular cartilages are shown, but the contour of the brain is indicated; and the manner in which the longitudinal muscles, which represent the anterior myotomes of Amphioxus, are arranged is shown. The tentacles of Amphioxus are represented by the tentacles of the Ammocwte, the hood-like " upper li p " of the latter obviously answering to the median prolongation of the head of Amphioxus with the two lateral folds of inte gument which lie outside the bases of the tentacles and are continued back into the ventro-lateral ridges. The relative shortening of the notochord, and lengthen^ ing of that region of the brain which lies in front of the origins of the optic nerves, in C, as compared with B, is remarkable. A line is drawn in all the figures through the anterior margin of the nasal sacs (N oN o); another has the same relation to the eyes (O p-O p); and a third (H y-H y) passes through the region of the auditory sac and hyoidean arch. 1, 2, 3, hyoidean and first and second branchial clefts of Ammoccetes; i., ii., in., iv., &c., myotomes of Amphioxus; M y, myelon or spinal cord; Ch, noto chord.