. Annotationes zoologicae japonenses / Nihon do?butsugaku iho?. NOTE ON A NEW DEEP-SEA EC HIU ROI», PROTOIJONELLIA M1TSUKURII, 263 oogonium of various growth-phases has at its free end a cap of a compact nutritive cell-mass, appearing, as in Bonellia, as a small cone with blunt apex. Fully grown oogonia of about mm. in diameter found in the coelom or in the oviduct are also accom- panied with the cell mass which has be- come a little reduced in size. Segmental organ or oviduct.—Only the left oviduct is present attached close to the ventral nerve-cord (fig. 2, od.). It is cocoon-shaped, th
. Annotationes zoologicae japonenses / Nihon do?butsugaku iho?. NOTE ON A NEW DEEP-SEA EC HIU ROI», PROTOIJONELLIA M1TSUKURII, 263 oogonium of various growth-phases has at its free end a cap of a compact nutritive cell-mass, appearing, as in Bonellia, as a small cone with blunt apex. Fully grown oogonia of about mm. in diameter found in the coelom or in the oviduct are also accom- panied with the cell mass which has be- come a little reduced in size. Segmental organ or oviduct.—Only the left oviduct is present attached close to the ventral nerve-cord (fig. 2, od.). It is cocoon-shaped, thin-walled, and provid- ed with a short stalk. The whole struc- ture measures about mm. long and about mm. thick. It seems however to have been a more spacious sac in the living state. The internal aperture of the organ is of a similar shape and posi- tion as is known in Bonellia ; it is a wide and notably fimbriated funnel attached to the distal end of a slender tube. The latter opens into the sac near the stalk or duct of the organ. The sac is filled with full grown spherical eggs of about mm. in diameter. Systematic position.—From the foregoing description, it will be seen that this species bears, so far as the internal anatomy is concerned, close affinity to the Echiuroids belonging to the genus Bonellia. It agrees very closely in almost all essential characters with the female form of Bonellia, viz., with respect to the ventral hooks, the alimentary canal, the anal glands, the vascular system, the single oviduct, and ovarian eggs. The only point of difference from Bonellia is in the shape of the proboscis. But it must here be noticed that the proboscis of the Echiuroids in general is a structure which varies more or less even in one and the same genus. Echinrus unicinctus for instance, is almost proboscisless as compared with other Echinrus species ; just the reverse is the case with Thalassema tacni- oides, in which the organ can be extended to a length t
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Keywords: ., bookcentury1800, bookcollectionbiod, bookdecade1890, bookyear1897
