Download e-book for iPad: Biology of Earthworms by C.A. A Edwards

By C.A. A Edwards

ISBN-10: 0412149400

ISBN-13: 9780412149405

ISBN-10: 1461333822

ISBN-13: 9781461333821

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The paired ovaries, which produce oocytes, are roughly pearshaped in Lumbricus (or fan-shaped in Pheretima), and are attached by their wider ends to the ventral part of the posterior face of Longltudma l muse Ie 10 yer =1I5iliii• • •} Ventrol ~ ~r Spermotheco Fig. IS Testes Sperm funnel Overy Ovonon funnel Vas deferens Diagram of the reproductive system from the side. (After Stephenson, 1930) septum 12/ I 3, hanging freely in segment 13 in most terrestrial worms. The ovisacs are backward-facing evaginations of the anterior face of the septum immediately behind the ovaries and open into the dorsal wall of the ovarian funnels.

The bases of the cells end as processes, one of which extends as a nerve fibre along the basal membrane and joins the nearest epidermal nerve. Proprioceptor cells situated in the muscle layers act as tension or stretch receptors. I3 The reproductive system Oligochaetes are hermaphrodite, and have more complicated genital systems than unisexual animals. The reproductive organs, which are confined to comparatively few segments in the anterior portion of the body (Figs 8, 15 and 16), include the male and female organs and associated organs, the spermathecae, the clitellum and other glandular structures.

Anteriorly, it passes into a suboesophageal ganglion, then bifurcates into the circumpharyngeal (circumCerebrol ganglion 4 5 6 Circumphoryngeol connectives FIg. 13 Anterior part of the nervous system from the side. (After Hess, 1925) oesophageal) connectives, which pass up round either side of the oesophagus, and meet as the bilobed cerebral ganglion on the dorsal surface of the pharynx in segment 3 (Fig. 13). Structurally, the ventral nerve cord is really a backward extension of the two circumpharyngeal connectives, fused together.

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Biology of Earthworms by C.A. A Edwards

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