. Anatomy, descriptive and applied. Anatomy. 1424 THE URINOGENITAL ORGANS other hand, maintains that in the skate they are not derived from this epithehum, but arc probably formed during the later stages of cell cleavage, before there is any trace of an embiyo; and a similar view was advanced by Nussbaum as to their origin in amphibia. Beard says: "At the close of segmentation many of the future germ cells lie in the segmentation cavity just beneath the site of the future embryo, and there is no doubt they subsequently wander into ; The germ cells, "after they enter the resti
. Anatomy, descriptive and applied. Anatomy. 1424 THE URINOGENITAL ORGANS other hand, maintains that in the skate they are not derived from this epithehum, but arc probably formed during the later stages of cell cleavage, before there is any trace of an embiyo; and a similar view was advanced by Nussbaum as to their origin in amphibia. Beard says: "At the close of segmentation many of the future germ cells lie in the segmentation cavity just beneath the site of the future embryo, and there is no doubt they subsequently wander into ; The germ cells, "after they enter the resting phase, are sharply marked off from the cells of the em- bryo by entire absence of mitoses among ; They can be further recognized by their irregular form and amoeboid processes, and by the fact that their cytoplasm has no affinity for ordinary stains, but assumes a brownish tinge when treated by osmic acid. The path along which they travel into the embryo is a very definite one—viz., "from the yolk sac upward between the splanchopleure and gut in the hinder portion of the ; This pathway, named by Beard the germinal path, "leads them directly to the position which they ought finally to take up in the 'germinal ridge.'" A considerable number apparently never reach their proper desti- nation, since "vagrant germ cells are found in all sorts of places, but more particularly on the ; Some of these may possibly find their way into the germinal ridge; some probably undergo atrophy, while others may persist and become the seat of dermoid tumors. Ovarian tube of epithelium. Blood-v Graafian —Germinal epithelium. Primitive ova. -Cell nest. Fig. 1202.—Section of the ovary of i vborn child. (Waldeye The testis is developed in a very similar way to the ovary. Like the ovary, in its earliest stages it consists of a central mass of connective tissue covered by germinal epithelium, among which larger cells, the primiti
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectanatomy, bookyear1913
