. Chordate morphology. Morphology (Animals); Chordata. epididymis vas deferens posterior end of Leydig's gland urogenital gland urogenital pore. Mullerion duct ampulla nterrenal gland openings of ureters A B C Figure 10-49. Urogenital systems of the chimaerid, Hydro/ogus. A, kidneys of adult female (see Figure 9-25 for relationships to reproductive tract and viscera in general); B, ventral view of mole systems, showing testes lying in anterior port of body cavity; C, laterol view of male systems. single band (25 to 30-mm larva). The stroma surrounding the gonocytes, or germ cells, appears to b
. Chordate morphology. Morphology (Animals); Chordata. epididymis vas deferens posterior end of Leydig's gland urogenital gland urogenital pore. Mullerion duct ampulla nterrenal gland openings of ureters A B C Figure 10-49. Urogenital systems of the chimaerid, Hydro/ogus. A, kidneys of adult female (see Figure 9-25 for relationships to reproductive tract and viscera in general); B, ventral view of mole systems, showing testes lying in anterior port of body cavity; C, laterol view of male systems. single band (25 to 30-mm larva). The stroma surrounding the gonocytes, or germ cells, appears to be of epithelial ori- gin but could include cells from the mesenchyme of the kid- ney anlage. The gonadal ridge extends through the posterior two-thirds of the body cavity, reaching almost to the poste- rior end. According to Lubosch (1903), about 25 per cent of the larvae have hermaphroditic gonads but later become males by loss of the ovocytes. Of adults, half are of either sex. In the male the clumps of germ cells form follicles, which when ripe rupture into the body cavity. In the female the germ cells become surrounded by follicle cells of the stroma which contribute to the development of the egg. The eggs rupture into the body cavity at maturity. The sex cells leave the body by way of the abdominal pores. These bilateral apertures in the wall of the urogenital sinus are similar in the two sexes. They open a few weeks before spawning. Injection of oestrone or anterior pituitary will cause perforation of these pores in the young lamprey. Myxinid The single gonad appears late as a structure at- tached to the gut just to the right of the mesentery. The an- terior part develops first and produces ovocytes; the poste- terior part develops first and produces ovocytes; the poste- rior part produces spermatocytes. In fish less than 20 cm long, none can be identified as males, but by 24 cm the two sexes are defined. However, both have a rudimentary area In the adult t
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