. Quarterly journal of microscopical science. ryo establishes these facts beyond also shows US that the neuromeres, no less than theembryonic coelomic cavities, point to the existence of one,and only one, prosthomere in Peripatus, of which the^Protocerebrum, P, is the neuromere, whilst the Deutero-cerebrum, D, is the neuromere of the second or buccalsomite. A brief indication of these facts is given by sayingthat the Onychophora are deuterognathous,—that is tosay, that the buccal somite carrying the mandibular hemi-gnaths is the second of the whole series. STRIJCTUEE AND CLASSIFICATIO
. Quarterly journal of microscopical science. ryo establishes these facts beyond also shows US that the neuromeres, no less than theembryonic coelomic cavities, point to the existence of one,and only one, prosthomere in Peripatus, of which the^Protocerebrum, P, is the neuromere, whilst the Deutero-cerebrum, D, is the neuromere of the second or buccalsomite. A brief indication of these facts is given by sayingthat the Onychophora are deuterognathous,—that is tosay, that the buccal somite carrying the mandibular hemi-gnaths is the second of the whole series. STRIJCTUEE AND CLASSIFICATION OF THE ARTHROPODA. 547 What has become of the nerve-ganglion of the prostoniiallobe of the Cha)topod in Peripatus is not clearly ascertained,nor is its fate indicated by the study of the embryonic headof other Arthropods so far. Probably it is fused with theprotocerebrum, and may also be concerned in the history ofthe very peculiar paired eyes of Peripatus, which are likethose of Chastopods in structure—viz. vesicles with an intra- ant. Fig. 3.—Diagram of the liead and adjacent region of m, Moutli; I, ccelom of first somitewhich carries the antennae, and is in front of the mouth; II, ccelomof the second somite, which carries the mandibles (lience deutero-gnathous); III and IV, ccelom of the third and fourth somites;, rudimentary frontal processes, perhaps representing the pro-stoniial tentacles of Poljchseta; ^?i^, antenna or tactile tentacle; Md,mandible; Oj?, oral i)apilla; P, protocerebruni or foremost cerebralmass belonging to the first somite; D, deulerocerebrum, consistingof ganglion cells belonging to the second or mandibular somite.(After Goodrich.) vesicular lens, whereas the eyes of all other Arthropods haveessentially another structure, being cups of the epidermis,in which a knob-like or rod-like thickening of the cuticle isfitted as refractive medium. In Diplopoda (Julus, etc.) the results of embryologicalstudy point t
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