[Structure of the copulative apparatus of Sobolevicanthus gracilis (Cestoda: Cyclophyllidea)].

Fine structure of genital atrium, Furman body, distal region of vagina and sac cirrus were investigated. The broad polymorphism of surface microstructures (microtriches) in various parts of copulative apparatus has been revealed. The constitution of prostate glands, being the modified cytons of syncitial epithelium of the intrabursal section of spermaduct wall, is described. Based on obtained and reference data, a comparative morphological analysis of copulative apparatus organization in lowest and highest cestodes was carried out. The hypothesis suggests that evolution of its organization was connected with the reduction of the muscular elements and simultaneous improvement of their managing, their isolation from surrounding parenchyma and development of supporting connective tissue elements. It is shown, that Fuhrmann's body has its own developed muscular system armed with power microtriches and being capable to evaginate into the distal region of vagina. It is supposed that S. gracilis obtains of two different ways of copulation in: by means of cirrus that executes the cross fertilization; and by means of the additional copulative formation--Furman body, which guarantees the self fertilization of worms.