THE Quarterly Journal of Microscopical Science for March 1892, contains:—On a new branchiate Oligochæte (Branchuira soweirbyi), by Frank E. Beddard, M. A. (plate xix.). This annelid, found in mud from the “Victoria regia tank” in the Royal Botanical Gardens, Regent's Park, London, is remarkable for the unusual contractility of its body, which suggested a leech or flat worm rather than a Chtætopod. It consists of about 120 segments. When magnified the orange-coloured digestive tract traversed by the bright blood vessels is seen, and at the posterior end of the body there is a series of delicate dorsal and ventral processes; these latter are segmentally arranged, developed in pairs upon the last sixty segments or so of the body. There is no connection between the setae and these processes, as in Bourne's Chætobranchus, also found in the same tank. This worm is referred to the Tubificidæ, without having any certain affinities to any of the known genera.“On the formation of the germ-layers in Crangon vulgaris, by W. F. R. Weldon, M.A. (plates xx. to xxii.). The author's conception of the early development differs widely from that of Kingsley.—On the pigment cells of the retina, by I. S. Boden and F. C. Sprawson. The retinal pigment cells are not, as usually represented, invariably hexagonal; in specimens taken from the eyes of sheep, ox, rabbit, kitten, pig, hen, and frog, while hexagonal cells were the most numerous, heptagonal cells were frequently found and scattered at intervals. Cells with tour, five, eight, nine, ten, and eleven sides were found.—Observations upon the development of the segmentation cavity, the archenteron, the germinal layers, and the amnion in mammals, by Dr. Arthur Robinson (Plates xxiii. to xxvii.). There is a general description of the development of the ova of the rat and mouse up to the period of the completion of the blastodermic vesicle, and a comparison with the results obtained by Fraser, Duval, and Selenka: there is a description of the formation of the mesoblast and of the chorda dorsalis, followed by a comparison of the ova of the rat and mouse with the ova of other mammals and the lower vertebrates and by a description of the formation of the amnion and a discussion of the relation of amnion formation to “inversion,” and by a description of the formation of the cœlom.
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