. Comparative anatomy of vertebrates. Anatomy, Comparative; Vertebrates -- Anatomy. 320 COMPARATIVE MORPHOLOGY OF VERTEBRATES. Ovaries. — In the ovarian epithelium the primitive ova multiply, and the products, accompanied by some of the epithelial cells, sink into the deeper stroma of connective tissue, thus forming ovarial cords each containing a number of ova. Then the cords break up and each egg becomes surrounded with a layer of epithelial cells, the whole forming a Graafian follicle, the follicle cells supplying nourishment to the contained ovum. In the higher vertebrates there is a great
. Comparative anatomy of vertebrates. Anatomy, Comparative; Vertebrates -- Anatomy. 320 COMPARATIVE MORPHOLOGY OF VERTEBRATES. Ovaries. — In the ovarian epithelium the primitive ova multiply, and the products, accompanied by some of the epithelial cells, sink into the deeper stroma of connective tissue, thus forming ovarial cords each containing a number of ova. Then the cords break up and each egg becomes surrounded with a layer of epithelial cells, the whole forming a Graafian follicle, the follicle cells supplying nourishment to the contained ovum. In the higher vertebrates there is a great increase in the number of follicle cells, which become arranged in several layers. Then a split arises in the follicle, the cavity becoming. -m 4 'C- ' T- ' •Vi' ° ^^V^S ' *J J/ - '%\V*v^^ FIG. 324.—Section of genital ridge of chick of five days' incubation, after Semon. e, epithel- ium of ridge (ccelomic wall); c, medullary cords; o, primordial ova. filled with a follicular liquor, while the ovum, surrounded by several layers of cells, adheres to one side of the cavity, this part being called the discus proligerus. When the eggs have attained their full size and the proper time has arrived some of the follicles migrate to the surface of the ovary, then the follicles rupture and the contained ova escape into the coelom. Their history from this point will be outlined in connection with the genital ducts. Each ruptured follicle (at least in elasmobranchs, amphibians and amniotes leaves a scar on the surface of the ovary— the corpus luteum—characterized by the presence of peculiar ('lutein') cells. Testes.—In the gonads of the male (testes) there is a somewhat similar insinking of the primordial ova and epithelial cells into the stroma of the genital ridge, but, instead of breaking up into separate follicles, each sexual cord develops a lumen and becomes converted. Please note that these images are extracted from scanned page images that may have been digitally enhan
Size: 2177px × 1148px
Photo credit: © The Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1910, booksubjectanatomy, bookyear1912
