SPECIES OF MARINE PLANARIANS. 85 



impaired value. Of my own drawings I can, of course, vouch for the faithfulness. They 

 were always taken from the living animal while in health and activity ; and any thing 

 striking and remarkable could not fail to be noticed and recorded. 



The term Planaria, which was at first applied to these animals as a generic name for 

 them all, has been long since restricted to a small division of them which is not marine. 

 Linngeus, Pallas, Lamarck, and Cuvier placed them among parenchymatous Entozoa ; 

 but the investigations of Duges, von Baer, Quatrefages, and others have by degrees raised 

 them to their proper and natural position. This is now assigned to them under the 

 Turbellarian Annelids. The genera described by Ehrenberg and De Quatrefages out of 

 the old genus JPlanaria have in turn for the most part been split up or given place to 

 more recent classification. I have endeavoured to assign positions to the present species 

 under the arrangement of Diesing (' Systema Helminthum'), as revised by W. Stimp- 

 son in his " Prodromus descriptionis animalium evertebratorum " of the South- Pacific 

 Eederal Expedition, under Capt. Jno. Rodgers (Proc. Acad. Nat. Scien. Philad. 1857, 

 p. 19 &c). Stimpson enumerates thirty-eight genera of Turbellaria Dendrocoela (Max 

 Schultze, Wiegm. Arch. 1849, p. 292), including several new genera resulting from that 

 expedition. Of these thirty-eight genera, eight are fluviatile, four terricolous, one inhabits 

 brackish water, and one is pelagic. The remaining twenty-four consist of ordinary marine 

 genera, under which group the present species would be all included. I have ventured 

 to constitute a new genus of two of the Ceylon species, from a character which does not 

 appear to be shared with any of those previously described. Inasmuch, however, as all 

 the Ceylon species have already been named by their collector and delineator, I shall 

 of course adopt his specific terms, only inserting them in what appears to me to be their 

 proper generic group. 



The marine Turbellaria Dendrocoela are for the most part flat, thin, soft, and delicate 

 animals, remarkable for their beautiful colours and often graceful forms and movements. 

 They have usually a pair of tentacles, these occasionally being mere folds or ear-like projec- 

 tions of the anterior margin (Euryleptidse) — sometimes true tentacles, situated occipitally 

 (Stylochidse), or even dorsally, in which case they are retractile (Planoceridse). In some 

 families, however, tentacles are entirely absent (Typhloleptidae and Leptoplanidse). The 

 margin is usually ample, and much folded or puckered, which is very noticeable when 

 the animal is at rest; but when in motion, this ample pallium is gracefully waved 

 in a vertical direction, and aids greatly such species as are natatory in swimming, 

 which they effect with ease and rapidity. They possess either two genital apertures (sub- 

 tribe Dlgonopora), as is the case with all the present species, or only a single one (sub- 

 tribe Monogonopora), as is the case with the true Planariadse. The mouth is variously 

 situated on the median line of the under surface, and is in turn antecentral, subcentral, 

 or postcentral ; and the dendriform gastrovascular ramifications are often more or less 

 visible upon the under surface. 



One of their most peculiar characteristics consists of the eye-spots, small black specks 

 of varying size and position, sometimes clustered into congeries of a symmetrical form, 

 and sometimes scattered over the anterior and marginal portions of the upper surface, or 

 on the tentacles. These eye-spots, in some cases at least, consist of a highly refracting 



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