OCR Text |
Show 1903.] POLYCLADS OF THE " SKEAT EXPEDITION." 303 Mr. Evans on the shores of the island of Pulau Bidan, where it is evidently one of the commoner species. The body of this worm is rather elongated, rounded in front and with a pointed hinder extremity. The arrangement of its eye-spots is shown in the accompanying figure (text-fig. 50). Text-fig. 50. # • Eye-spots of Notojplanci evcinsii. Unfortunately I have no notes as to colour, but, judging from the spirit-specimens, the creature is probably of a yellowish-grey colour, with a small number of irregularly scattered black spots. The gut-branches are numerous, and there is no anastomosis. The dimensions of an average individual are as follows :- Length............................................... 25 mm. Breadth............................................ .. 15 ,, Tentacles from ant. margin............... 5 ,, Mouth-opening ,, ........... 12 ,, <S . Aperture behind mouth ........... 3'5 ,, 2 • ,, behind male............... 1*5 ,, Genital Apparatus (see text-fig. 51, 304). The most striking features of the male copulatory apparatus are the great length of the antral chamber and the chambered prostate organ, the latter recalling the prostate of certain Leptoplanas, e. g. L. alcinoi. From the male aperture the antral cavity (text-fig. 51, a.m.) extends forwards as far as the level of the hinder end of the pharynx. It has very muscular walls and runs sloping in an upward direction. Lang, in his diagram of the genital apparatus of Hoploplana (Planocera insignis group [6]), calls this chamber the penis-sheath (" Penisscheide), but this term should, I think, be reserved for the sheath-like folds of the walls of the antral chamber occurring in Cestoplana and in certain Cotylea.n genera. The lining of the walls of the antral chamber in the present species consists of a flattened ciliated (?) epithelium ; the muscular wall consists of a thick layer of interlacing circular fibres. P r o c . Z o o l . S o c .- 1893, Y o l . I. No. X X . 20 |