Das System der Polycladen. 501 



specimeiis were very small, measuring ouly about 3 mm iu leugtli. Tliey weve evidently very youug, haviiig 

 as yet iio tracc of generative organs, aud the tissues not yet well defined. • — Tlie body was ovoid in form, 

 and completely flattened. The posterior cxtremity narrowed to a bliint point. Tentaeles were absent. — 

 In the centre of the anterior extremity was a slight depression or pit, appareiitly an orgau of seuse, and 

 whifh seemed to be used by the animal as such. — The mouth is elongate aud folded, and large in pro- 

 portion to the size of the body, as usual in young planariaus. The ramifications of the digestive tube were 

 already marked out, thongh not very distinctly. The forward Prolongation of the niaiu digestive tube passes 

 as usual over the nervous ganglia. The eyes were disposed in two irregulär semicircles situate one on either 

 side of the ganglia, with their convex side towards the latter. In one specimeu there were twelve eye-spots 

 ou one side and eleven on the other ; in the other eight on each side. A posterior group of three eyes on 

 either side was in both of the specimens, separated from the remainder by the passage between it and them 

 of the last brauch given off by the main digestive tube before it jjasses over the ganglia. These groups of 

 eyes seem to be homologous Avith those situate at the bases of the tentaeles of Stylochus pelagicus. — The 

 most interestiiig point about the present form is that the eyes appear to have definite directions which cor- 

 respond exactly ou the two sides of the body. In the above described posterior group of eyes this eon- 

 dition was especially marked, and was seen in both specimens of the animal. Here the most posterior eye 

 looks directly forwards, the one directly anterior to it directly iuwards, aud the outer one of the group 

 obliquely inwards and backwards; five of the remaining eyes look directly upwards; the others have definite 

 directions, as may be seen in the figure. The arrangement of the most auterior was not quite synuuetrical. 

 In the second specimeu of the animal with but eight eyes on either side, the posterior group had uearly 

 the same directions as in that just described. All of them showed direction towards definite points. — The 

 specimeu with twelve eyes on either side was of a uniform pale whitish colour. The other specimeu had 

 its Upper surface covered with scattered, round, small, brownish pigment spots. Both specimens were very 

 lively, swimmiug by undulatiou of the body margin. — This planarian, from the seas of the East Indian 

 Archipelago, being devoid of tentaeles, seems to indicate another new pelagic species, which possibly should 

 be referred to the geuus Leptoplana, but as only very young specimens were obtained, the evidence is in- 

 sufficient.« 



Vermuthlich gehört auch die folgende, von Darwin aufgefundene Polyclade in das 

 Genus Leptoplana. Wahrscheinlich ist eine der zwei von Darwin erwähnten Mundöfihungen 

 ein zufölhger Kiss in der Körperwand in der Gegend der Pharyngealtasche. 



75. Leptoplana (Ehrenberg) ? notabilis (Darwin) mihi. 



Diplanaria notabilis, Darwin 1844. 41. pag. 249 — 250. Tab. V. Fig. 4. 

 ? Diplanaria notabilis, Diesing 1850. 56. pag. 202. 

 Leptoplana notabilis, Diesing 1862. 89. pag. 542. 



»Body very much depressed, with the edges very thin : anterior extremity thricc as broad as the 

 posterior. On the under surface, towards the anterior extremity, there is a clear space, over m hieb, on the 

 back, the ocelli are situated; into this space, on all sides, the branching, clear, intestinal cavities enter. 

 Each intestinal cavity generally bifurcates three times before its fine extremities reach the margin of the 

 body. Towards the posterior extremity there is a second clear space (with the two orifices D aud E) into 

 which also the surrouuding intestinal brancliing cavities euter; these two Spaces are united by two longi- 

 tudinal clear Spaces (obscured by ovules in the drawiug) passing on each side of the elongated, opake, white, 

 central organ. This organ, when the animal is contracted, has the appearance rejjresentcd in the drawing, 

 namely of au internal, eUiptic mass, narrowing at each eud, with deeply sinuated borders, and with two 

 cxterual, perfectly closed orifices over it, as sho-mi at (5) and (C). But when these two oiifices are opened, 

 from both of them broad, sliallow, saucer-like moutli-suckers are protruded , as represented at {F\ : these, 

 when contracted within the body, appear united, and form a single, elliptic , sinuated body. These two 



