. The Annals and magazine of natural history; zoology, botany, and geology. Natural history; Zoology; Botany; Geology. 442 Prof. A. Schneider on the Develojjment The embryo, or, rather, the hirva proceeding from it, divides very soon into two haycrs, a thick dermal Layer and an inner cell-mass, from whicli the other organs originate. The dermal layer is characterized by very large spherical nuclei with nuclear corpuscles : these at first lie irregularly scattered, but they then aiTange themselves in the following manner:—At the cephalic extremity a band of six nuclei is formed, between •which
. The Annals and magazine of natural history; zoology, botany, and geology. Natural history; Zoology; Botany; Geology. 442 Prof. A. Schneider on the Develojjment The embryo, or, rather, the hirva proceeding from it, divides very soon into two haycrs, a thick dermal Layer and an inner cell-mass, from whicli the other organs originate. The dermal layer is characterized by very large spherical nuclei with nuclear corpuscles : these at first lie irregularly scattered, but they then aiTange themselves in the following manner:—At the cephalic extremity a band of six nuclei is formed, between •which the six foremost hooks protrude. A second band, of about fourteen nuclei, is formed at the place where the lemnisci are produced. The nuclei of this band become the nuclei of the lemnisci: while the latter grow inwards as two processes of the skin, the nuclei graduallj'- pass into them. Of the remaining nuclei the hindmost four, with their nuclear cor- puscles, increase considerably in length, and accompany the lateral lines of the body on each side as four cords. In the mature state they attain nearly the whole length of the body, and are probably the longest nuclei known. Between the lemniscal band and the anterior extremities of these four nuclei, a considerable number of nuclei are rather irregularly placed; these also increase in length, but in a much less degree. All these long nuclei, as also their nuclear corpuscles, give off short acute diverticula on both sides. These large, long nuclei are still found in the mature exam- f)les. Without the history of the development, their morpho- ogical signification could hardly be guessed. Both the ovaries and the testes are produced extraordinarily early. The former are two bodies, each composed of about four cells, and are both situated at tlic same place. Each testis is connected by a cord, consisting of a series of cells (afterwards the efferent duct), with the well-known muscular vas deferens. The ovaries are from the fir
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