400 Miscellaneous. first and seventh arches; on the others the fringes are developed from the outer and convex portion of the arch, and are not at first I)rolongations of the internal gills. (6.) The nostrils, as in all Vertehrates, consist at first of pits or indentations in the integuments ; secondly, a lohe is developed on the inner border of each ; and, finally, the two lobes become con-nected, and thus form the homologue of the fronto-nasal protu-berance. The transitional stages of these correspond with the adult conditions of them in other species of Selachians. (7.) The nasal grooves arc compared with the nasal passages of air-breathing animals, and the cartilages on either side of these to the maxillary and intermaxillary bones. (8.) The foremost part of the head is formed by the extension of the facial disk forward. While this extension is going on, the cere-bral lobes change their position from beneath the optic lobes to one in front of them. (9.) Two anal fins, one quite large and the other very small, are developed, but both are afterwards wholly absorbed. (10.) The dorsals change position from the middle to the end of the tail. At the time of hatching, however, there is still a slender terminal portion of the tail, which is afterwards either absorbed or covered up by the enlarged dorsals, as they extend backward. — Memoirs of the American Academy, vol. ix. pp. 31-44. On Dimorphism in the Hrjmenopterous Genua Cynips. By Benjamin D.Walsh, M.A. The Cynips studied by Mr. Walsh make galls on a species of oak, the Quercus tinctoria. Part of these galls produce males and fe-males of the Cynips spongijica in June. Another portion of them, of wholly similar general character, remain green till autumn, and produce in October and November, and also in the following spring, another form of Cynips — the Cynips aciculata, hitherto regarded as a distinct species, all the individuals of which are females. Mr. Walsh appears to prove that the latter, although widely different in many characters, is only another form of the C. spongificu, and thence that this species is dimorphous. The individuals produced in June live but six or eight days ; what place in nature, then, tlie author asks, is filled by the C. aciculata 1 In reply, he suggests, from the analogy of Apis, Bomhus, &c., that " the female aciculata gene-rates galls, which produce by parthenogenesis male sponyifica, and that the females and males of the latter, coupling in June, oviposit in the same month, in the young buds of the oak, eggs that remain dormant till the following spring, some of which then produce /e/«a/e sponyifica in June and some female aciculata in the autumn or early in the following spring, and these last, in their turn, generate male sponyifica to appear in the following June." He continues, " It may also be the case that some few male sponyifica are generated by fe-male sponyifica.'" The author next sustains this opinion by men-tioning some of the analogies that have been observed in other Hymenopterous insects. — Proceedinys of the Entomoloyical Society of Philadelphia, March 1864, pp. 443-500.