SANGUIFEROUS SYSTEM. 437 



together with the ramified cceca of the alimentary canal, the 

 two long convoluted ovaries, (132. i. k. /,) the capacious sin- 

 gle oviduct, (132. m. n. o,) the testicle (132. /?,) and the spiral 

 vas deferens (132. g,) occupy the greater portion of each ab- 

 dominal cavity. The oviducts have distinct openings (132. o) 

 at the inner margin, near the proximal end of the two poste- 

 rior divisions of the animal, like the marginal genital open- 

 ings of the tcenia. The four firm, cartilaginous, oval disks, 

 by which the animal attaches itself to the surface of the gills, 

 are provided each with four suctorial cavities (132. b. s.) j 

 they occupy the inferior margins of the wide posterior parts 

 of this bifid trunk, and these diverging parts terminate by an 

 expanded fold, with free reverted margins (132. a. a.), in 

 form of a valve or protecting mantle. Longitudinal and 

 transverse muscular fibres are obvious within the firm exte- 

 rior elastic skin, and the light yellow colour of the animal is 

 often changed to red, by the blood, sucked as food, filling 

 the ramified alimentary canal, and appearing distinctly 

 through the transparent texture of the body. The intestine 

 expands like a stomach across the place of junction of the 

 two lateral halves of this animal, but there is no distinct anal 

 opening in the body, and the residue of the digested blood is 

 often seen to be expelled by the buccal orifice, on disturbing 

 the diplozoon. 



The colourless and limpid serous fluid circulating in the 

 vessels of this animal is carried forwards by two upper, late- 

 ral arterial trunks (132. u. u. v. v.) in each segment of the 

 body, and it is returned backwards by two corresponding, 

 inferior lateral veins, (132. s. s. t. /.), but there is no cordi- 

 form dilatation on any part of the sanguiferous system, nor is 

 the slightest pulsation observed in any of the vessels. As 

 in similar minute ' transparent animals, the ramifications and 

 anastomoses of the arteries and veins, and the currents of the 

 blood are best seen through the microscope by transmitted 

 light, when unobstructed by opaque contents in the ovaries 

 or the alimentary cavities. The two great ventral venous 

 trunks (132. t. s.) of each segment are observed to commence 

 small near the sides of the oesophagus, where they soon re- 

 ceive the terminations of numerous peripheral and central 

 veins, collected from the neighbouring parts, especially of 

 two long lateral branches, extending forwards parallel to the 



