. Annual report of the Board of Regents of the Smithsonian Institution. Smithsonian Institution; Smithsonian Institution. Archives; Discoveries in science. 476 PARENTAL CAEE AMONG FRESH-WATER FISHES. Fig. r}6. —Ad- vanced Aspredo egg with pedi- fle of attacl^- men t ( ?; 4 ). After Wyman. could be made on the earlier conditions of the egg and the formation of its pedicle. The pedicle is a flexible outgrowth from the common integuuients, is about two lines in length, is attached to the skin by a slightly expanded base, and spreads out at its summit into a shallow cup or " ; for
. Annual report of the Board of Regents of the Smithsonian Institution. Smithsonian Institution; Smithsonian Institution. Archives; Discoveries in science. 476 PARENTAL CAEE AMONG FRESH-WATER FISHES. Fig. r}6. —Ad- vanced Aspredo egg with pedi- fle of attacl^- men t ( ?; 4 ). After Wyman. could be made on the earlier conditions of the egg and the formation of its pedicle. The pedicle is a flexible outgrowth from the common integuuients, is about two lines in length, is attached to the skin by a slightly expanded base, and spreads out at its summit into a shallow cup or " ; for the support of the egg. It is composed almost entirely of fibrous tissue, invested with a layer of tesselated epithelium. In some instances when the eggs were but little advanced, numerous fusiform cells were detected among the fibers. It is vascular, two or three vessels I'eaching to the cup, where they ramify and form a somewhat extended capillary plexus [flgs. 50 and 57]. The eggs vary according to the degree of development from to of an inch in diameter, and are covered with an external homogeneous membrane, containing minute puncti- form depressions—within this is a second, of a brownish color and composed of epithelium. The embryos which were the most advanced and just ready to hatch, had not as yet com- pletely absorbed the yolk, and were coiled up within the mem- liranes, which in consequence of the irregularities of the mass formed by the embryo had no longer a spherical form. The eggs are retained in connection with the cup apparently by adhesion alone, for as soon as the foetus escapes, the egg membranes become very easily detached from the pedicle, and this last as shown by some of the specimens undergoes absorption. The relation of the embryo to the parent in this singular mode of gestation can not be determined very accurately, but the vascular plexus in the cup seems to be more than is necessary for the mei*e nutrition of the part. The egg increase
Size: 993px × 2518px
Photo credit: © Library Book Collection / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookauthorsmithsonianinstitutio, bookcentury1800, bookdecade1840
