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Originariamente inviata da balabam
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Non è vero. Le physa si riproducono anche per parenogenesi.
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quali sono le fonti?
le phisa sono ermafrodite di certo,la partenogenesi non dico impossibile.... perchè esiste anche in animali più superiori, ma tale notizia non l'ho mai trovata da nessuna parte,anzi... in questo testo inglese si descrive l'anatomia di una physa in cui chiaramente si rileva la presenza di entrambi gli apparati sessuali.
ma potrei sempre sbagliare
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From the carrefour the oviduct (ov) emerges as a narrow tube which runs leftwards, gradually widens, becomes bosselated and highly convoluted, proceeding into the nidamental gland (ng). This latter shows no remarkable features and narrows to the uterus (ut) and vagina (va), which receives the spermathecal duct (sd), about twice as long as the spermatheca (sp).
Immediately after emerging from the carrefour the spermiduct gives off a series of short prostatic diverticula (pr). They are closely packed, so that their numbers are difficult to determine; in one thoroughly dissected specimen about 45 units were recorded. They may be simple or divided into usually 2-4 short branches. After giving off the last diverticulum the spermiduct continues into the vas deferens (vd), which opens into the caudal end of the penis. The penis sheath (ps) is somewhat swollen proximally, tapering gradually distalward and expanding into a sarcobellum at its junction with the prepuce. The penis, free within the penis sheath (ps), decreases in width toward its extremity, and has a terminal outlet (Fig. 4, pe). The prepuce (pp), much wider than the penis sheath, is from about as long to twice as long as the latter; a lenticular gland (pg) is present on the proximal half of the preputial wall. A set of retractor (rpc) and protractor (pm) muscles are inserted into the walls of the penial complex.
°???? altrimenti le metto anch'io nel bicchiere!!!! 
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