. An elementary course of practical zoology. Zoology. GONADS 409 end is a ciliated depression usually known as the olfactory pit (plf. p). There is no auditory organ. The dorsal and ventral nerves (Fig. 100 A, sn) remain separate, and do not unite to form a nerve-trunk (compare p. 163). The sexes are distinct, and the metamerically arranged gonads (Fig. 98-100, gon. g) are situated in pouches, the cavities of which represent part of the coelome and which project into the atrium on either side of the pharynx. When ph -"O^ Fig. ioi.—Diagram of th
. An elementary course of practical zoology. Zoology. GONADS 409 end is a ciliated depression usually known as the olfactory pit (plf. p). There is no auditory organ. The dorsal and ventral nerves (Fig. 100 A, sn) remain separate, and do not unite to form a nerve-trunk (compare p. 163). The sexes are distinct, and the metamerically arranged gonads (Fig. 98-100, gon. g) are situated in pouches, the cavities of which represent part of the coelome and which project into the atrium on either side of the pharynx. When ph -"O^ Fig. ioi.—Diagram of the vascular system o^ AviJ/hioxus. of. hr, a, afferent branchial arteries ; hr. cl. gill-slits ; cp. interstinal capillaries ; d. ao. paired dorsal aortee; d. clo'. median dorsal aorta; ef. br. a. 'efferent branchial arteries ; hep. port, v. hepatic portal vein ; hep. v. hepatic vein ; int. intestine ; Ir. liver ; ph. pharynx : s. int. v. sub-intestinal vein ; v. ao. ventra aorta. (From Parker and Haswell's Zoology^ rip^j^ the eggs and sperms are shed into the atrium and find their way out through the atriopore. The oosperm undergoes segmentation, and gives rise to a simple larva, which gradually develops into the adult form. The embryology of Amphioxus, which is very instructive, will be referred to in greater detail in Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Parker, T. Jeffery (Thomas Jeffery), 1850-1897; Parker, William Newton, joint author. London, Macmillan and Co. , Limited; New York, The Macmillan Company
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