\.QQ PROF. W. A. HASWELL ON AUSTEALASIAN POLYCLADS. 



raised wp into a number of longitudinal ridges. Behind the point where the median 

 uterine duct leaves it below a process of epithelium projects into the lumen ; this may, 

 perhaps, act as a valve for preventing the passage of the eggs backwards to the posterior 

 female aperture. 



The uteri are wide tubes containing, in the sexually active animal, numbers of ripe 

 eggs, together with quantities of spermatozoa. The eggs are all at the same stage. In 

 each is the usual centrally-placed spindle with four chromosomes. 



This appears to be the fourth Polyclad genus in which a second female aperture has 

 l)een discovered. But in other respects the four forms have very little in common. 

 Lang's genus Tr/'goiioporiis *, of which two American species — T. folium and T. deii- 

 di'iticus t — have been described by Verrill, has no tentacles, has numerous scattered 

 cephalic eyes, and has a separate prostate Avith independent duct. Of the affinities of 

 BergendaUa, Laidlaw, little is known, but in that genus the second aperture leads into 

 the antrum feraininuni. Laidlaicia, Herzig, has the aperture in question on the dorsal 

 instead of the A"eutral side, and there is a well-developed receptaculum seminis. In 

 Pohipoi-us, Plehn, there is a close correspondence in the relations of this aperture with 

 wliat we find in TripyloceUs. The single specimen of Tolyporus found was not sexually 

 mature, so that little was ascertainable regarding the reproductive apparatus ; but there 

 are pores all round leading into the intestinal branches, and there are no eyes. 



If Ave leave the occurrence of the third reproductive aperture out of account the closest 

 relationships of Tripylocelh are with the Planoeeridse. The members of Lang's grouj) B 

 of the species which he referred to the genus Phmocera are, apparently, the nearest 

 relatives. But the relationship is by no means very close, the differences in the male 

 reproductive apparatus being very considerable. 



TripyloceUs tijpica is perhaps the commonest Polyclad that occurs between tidal limits 

 in Port Jackson. It is chiefly to be found in tidal pools among the thalli of TJlva and 

 can usually be obtained in considerable numbers by iiulliug the Algge to pieces and 

 shaking them out in a vessel of water. 



It is an extremely active form, swims vigorously, and on the surface of a solid object 

 is able to progress rapidly by advancing lateral lobes, Avhich are able to adhere to the 

 siirface, and are pushed forward from right and left sides alternately — the result being 

 a kind of "walking," as distinguished from " creeping " or " looping" locomotion. 



The following is a definition of the genus TripyloceUs : — 



Planoceridse with fairly broad, oval, leaf-shaped body, Avith conical non-reti"actile 

 tentacles. Brain-tentacles and eyes relatively further forward than in Planocera — in 

 the first firth, or thereabouts. Two groups of tentacular eyes, and smaller eyes just in 

 front of and behind the brain ; no marginal eyes. Three genital apertures. Male 

 aperture a considerable distance behind the pharyngeal sac. Principal female aperture 

 not far behind the male : second female aperture on the ventral surface not far behind 

 the first. Penis miiscular, Avithout sheath and Avithout chitinous parts. A small median 



» 1 7, 1). .502. 



t As pointed ou( by Laidlaw (14), the generic position of these is doubtful. 





