. Elementary text-book of zoology, tr. and ed. by Adam Sedgwick, with the assistance of F. G. Heathcote. FlO. 292.—Embryo of Echin- orhynchug g>gus enclosed in the egg membranes (after Leuckurt). and 291, Li}. The sexes are separate. The male (fig. 290) has two testes (T), and the same number of efferent ducts (Vd). The latter unite behind to form a ductus ejaculatorius (De), which is often fur- nished with six or eight glandular sacs (Pr), and a conical penis (P), at the bottom of a bell-shaped protrusible bursa (7?), situated at the posterior pole of the body (fig. 290). The generative or
. Elementary text-book of zoology, tr. and ed. by Adam Sedgwick, with the assistance of F. G. Heathcote. FlO. 292.—Embryo of Echin- orhynchug g>gus enclosed in the egg membranes (after Leuckurt). and 291, Li}. The sexes are separate. The male (fig. 290) has two testes (T), and the same number of efferent ducts (Vd). The latter unite behind to form a ductus ejaculatorius (De), which is often fur- nished with six or eight glandular sacs (Pr), and a conical penis (P), at the bottom of a bell-shaped protrusible bursa (7?), situated at the posterior pole of the body (fig. 290). The generative organs of the larger females (fig. 291) consist of the ovary developed in the ligament; of a complicated uterine bell, beginning with a free opening into the body cavity ; of the oviduct and the short vagina, which is divided into several portions and opens at the posterior end of the body (fig. 291). It is only in the young stage that the ovary is a simple body en- closed by the membrane of the above-men- tioned ligament. As the animal increases in size, the ovary grows, and becomes divided into numerous spherical masses of eggs, the pressure of which bursts the membrane of the ligament; the masses of ova as well as the ripe elliptical eggs, which gradually become free from them, fall into the body cavity. The egg membranes are not formed till a. 7, c (^ d g^ after seg- mentation, and ought perhapsto be interpreted as embryo- nic mem- branes. The eggs, which already con- tain em- bryos, pass out of the body cavity into the uterine bell, which is continually dilating and contracting, thence into the oviduct, and through the genital opening to the FIG. 293.—Larvae of EcJiinorhyncJivi prof, 13 from Gamniarus (aftei Leuckart). a, Free embryo ; ETe, embryonic nucleus, b. Older stapo, •with more differentiated embryonic nucleus, c, Young female worm ; Ov, ovary, d, A young male worm ; T, testes; Le, Please note that these images are extracted from scanned p
Size: 1256px × 1988px
Photo credit: © Paul Fearn / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., book, bookcentury1800, bookcollectionbiodiversity, bookdecade1890
