. Catalogue of the Chaetopoda in the British Museum (Natural History). Oligochaeta; Polychaeta. 72 A renicolidae Eeproductive Organs. The reproductive organs are closely associated with the nephridia. Id the caudate species and in A. hranchialis the gonad is present a^ immediately behind the funnel of each nephridium, except the first, and is a small, ovoid or cylindrical mass of cells (PI. XIV, Figs. 48-50; PI. XY, Fig. 51) around the anterior portion or the whole length of the gonadial vessel,^ which is a continuation of the blood-vessel traversing the dorsal lip of the funnel. The genital p
. Catalogue of the Chaetopoda in the British Museum (Natural History). Oligochaeta; Polychaeta. 72 A renicolidae Eeproductive Organs. The reproductive organs are closely associated with the nephridia. Id the caudate species and in A. hranchialis the gonad is present a^ immediately behind the funnel of each nephridium, except the first, and is a small, ovoid or cylindrical mass of cells (PI. XIV, Figs. 48-50; PI. XY, Fig. 51) around the anterior portion or the whole length of the gonadial vessel,^ which is a continuation of the blood-vessel traversing the dorsal lip of the funnel. The genital products are shed at an early stage from the gonads into the coelomic fluid, and by an examination of this the sex of a given specimen is determinable. There the small groups of spermatogonia undergo repeated division and become succes- sively spermatocytes, spermatids and sperma- tozoa, large discoidal masses of which are present in the coelom of mature worms. The oocytes are shed from the ovary when they are about 12 to 20/i in diameter; while in the coelomic fluid their yolk is elaborated and they grow to the definitive size. The ripe ova of A. marina, pusilla, assimilis and cristata' are not spherical but biconvex (Fig. 42 b) ; the face of the ovum is either circular or oval and its two diameters are from '14 to "20 mm., while the third axis of the egg is about '08 mm. The vitelline membrane is comparatively thin, being 1 to 2/A in thickness. The ova oi A. hranchialis FiK^ .4.»,««•««. Ripe sper- find ecaudattt, which have a very stout Z^:^^Ti^^r^ vitelline membrane, 5 to 6/. in thickness, lifht: Tl tZJZi^^'^ are oval in shape and are each about o^"™- • 17 mm. long and • 15 mm. broad (Fig. 42 c). The reproductive organs of A. ecaudata are much larger and more complex than those of the other species, and form the most striking ' There is a gonadial vessel on the iirst nephridium, but a gonad appears never to be associated with it. ^ Probably also t
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