A reference handbook of the medical sciences, embracing the entire range of scientific and practical medicine and allied science . Fig. 1310.—Eggof Ttmia 380. (AfterLeuckart.) retained in the uterus of the adult ce.^tode. When theuterine egg is examined soon after its formation, theshell is seen to contain a single germ cell surroundedby a number of yolk cells which, in some cases, havelost their cellular identity and constitute merely amass of granular yolk substance. The embryo originates from the development ofthe egg cell alone while the yolk cells serve as nutri-. FlG. 1312.—Free
A reference handbook of the medical sciences, embracing the entire range of scientific and practical medicine and allied science . Fig. 1310.—Eggof Ttmia 380. (AfterLeuckart.) retained in the uterus of the adult ce.^tode. When theuterine egg is examined soon after its formation, theshell is seen to contain a single germ cell surroundedby a number of yolk cells which, in some cases, havelost their cellular identity and constitute merely amass of granular yolk substance. The embryo originates from the development ofthe egg cell alone while the yolk cells serve as nutri-. FlG. 1312.—Free O n c h o-sphere. Mag-nified. Fio. 1311.—Free Swimming Onchosphcre of Dibothriocephalua^/U5 ia ciliated mantle. XoOO. (After Schauinsland.) ment during its early growth. From the division ofthe egg cell, which undergoestotal cleavage, therearises a spherical embryo surrounded by one or moreenbryonic membranes. From the latter mayoriginate an inner shell, as is the case in Tajniadae (),oraciliatedmantle,asin Bothriocephalidae (). The spherical embryo (Fig. 1312), which isknown as the onchosphere, is uniformly characterizedby the presence of three pairs of hooks.^S^ of variable shape and by great mobil- ^ J ity, and in this condition is ready for \m^ introduction into the secondary host. This may be the result of a direct mi-gration, as when the ciliated bothrio-cephalic! embryo, swimming about inthe water, is swallowed by a suitablehost; or it may be of passive character, as when thetsenioid egg containing an embryo enveloped in itsmembranes arrives
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Keywords: ., bookauthorbuckalbe, bookcentury1900, bookdecade1910, bookyear1913
