478 PROF. ^Y. A. HASWELL OX AL'STEALASIAX POLTCLADS. 



elongated groups of tentacular eyes. Mouth lieliind tlie middle of the ventral surface. 

 Separate male and female reproductive apertures. A median vesicula, between which 

 and the penis is an elongated prostate reservoir. A very large penis without sheath, 

 lined internally with numerous chitinous teeth. Ventral limb of vagina (antrum and 

 ootype) with very thick walls. No dorsal limb present. Single unsymmetrical diverti- 

 culum projecting forwards from vagina. No receptaculum seminis. 



UcMnopkma celerrima is one of the commonest of the Polyclads of Port Jackson, It 

 is characterized by great alertness and activity. In addition to tlie ordinary swimming 

 and creeping movements, it progresses like Tripylocelis, but much more actively, by a 

 kind of " walking." Lateral lobes of the extremely mobile body assume the function of 

 lateral appendages. It is interesting to note that a precisely similar mode of locomotion 

 was observed by Lang in Flanocera Groffil, of which he writes — " Wenn Planocera 

 Graffii abwechselnd rechts und links Partien des vorderen Korperrandes vorstreckt und 

 dann den Ivtirper nachzieht so sieht es beinahe aus wie wenn sie sich derselben als Fiisse 

 bediente " (17, p. 635). 



Enterogonia PIGEA.NS, n. g., n. sp. (Plate 37. fig. 4.) 



. This Polyclad is of oval or elliptical outline, 1 cm. in length in the preserved condition 

 and 5 or G mm. in breadth. It is a thickish form, of comparatively firm consistency, 

 remarkable for its extremely sluggish movements. The general colour is greenish or 

 dark grey on the dorsal side ; wdien the living animal is examined with a simple lens, 

 this becomes resolved into innumerable spots of dark olive, very minute towards the 

 margin, larger towards the middle. The ventral surface is reddish grey, except where 

 the pharynx and main testicular ducts show white. In two of the specimens there is a 

 dark spot towards the posterior end — the appearance being produced by the intestinal 

 branches here being of a peculiarly dark colour. This does not appear to be constant ; 

 but when it does occur it probably is in some way associated with the occurrence of the 

 genito-intestinal passage referred to below. 



The mouth is considerably behind tlie middle of the body, and, in the fixed specimen, 

 the reproductive apertures are situated very close together, and are nearer to the posterior 

 edge than to the mouth. There are numerous scattered minute eyes over the brain- 

 region, and between the latter and the anterior margin, as well as marginal eyes running 

 all round the periphery. The eyes over the brain-region are quite irregularly distributed, 

 and not in any way bilaterally grouped, a feature which would in itself distinguish the 

 present species from Lang's Cestoplana alba and C. compacta (17, p. 472). 



The male aperture leads into a nea^rly vertical antrum, the epithelium of which is 

 thickened and raised into ridges. Here are situated the unicellular glands corresponding 

 to the prostate glands. Into the antrum projects the penis in the form of a short 

 muscular papilla entirely devoid of chitinous parts. The ejaculatory duct, formed by 

 the union of the lateral vasa deferentia, is a sinuous tube which presents no appearance 

 of becoming thickened or dilated to form a vesicula semmalis. 



The antrum femininum is a vertical chunaber with a fairly thick muscular wall. The 

 ootype curves forwards and iipwards from the antrum and bends sharply downwards and 



