On the Anatomy of the Land-Planar ians of Ceylon. 311 



With regard to the habits of Bipalium, the most interesting 

 facts noted are that these animals use a thread of their body- 

 sUme for suspension in air, as aquatic Planarians were observed 

 to do for their suspension in water by Sir J. Dalyell, and the 

 cellar-shig does for its suspension in air. The projection of 

 small portions of the anterior margin of the head in the form 

 of tentacles, originally observed by M. Humbert, becomes interest- 

 ing in connexion \^ith the discovery of a row of papillae and ciliated 

 pits in that region. The anatomy of the Planarians was studied by 

 means of vertical and longitudnial sections from hardened specimens. 

 The skin in Bipal'mm and RhpicJiodemus closely conforms to the 

 Planarian ty^e, but is more perfectly differentiated histologically 

 than in aquatic species, and approaches that of the leech in the 

 distribution, colour, and structure of its pigment, and especially 

 in the arrangement of the glandular system. The superficial 

 and deep glandular system of the leech are both here represented. 

 In B. Ceres peculiar glandular structures exist, which may fore- 

 shadow the segmentaj organs of Annelids, it being remembered 

 that these segmental organs are solid in an early stage of develop- 

 ment. Eod-like bodies (Stabchen or stabchenformige Korper) are 

 present in abundance, though, singularly enough. Max Schultze 

 failed to find any in Geoplana. These rod-like bodies are probably 

 homologous with the nail-hke bodies of Nemertines ; and it is pos- 

 sible that the setae of AnneUds are modifications of them. No 

 light is thrown by the structure of these bodies in Bipalium on 

 the question whether they are homologous with the urticating 

 organs of Ccelenterata, 



The musciilar arrangement in Bipalium, which is very complex, 

 throws great light on the homologies between the muscular layers 

 of Turhellaria and those of other Vermes. It is commonly said 

 that whilst in all other Vermes the external muscular layer is 

 circular, and the longitudinal internal, in Turbellarians the reverse 

 is the case. A wide gulf is thus apparently placed between these 

 groups. In Bipalium there is an external circular muscular coat, 

 which even presents the same imbricated structure which is found 

 in it in leeches and other worms. In Dendrocoelum lacteum there 

 is also an external circular coat. In cases where a distinct 

 external circular muscular coat is absent, it is represented by a 

 thick membrane, which is very probably contractile. The ques- 

 tion resolves itself simply into a more or less perfect fibrillar 

 differentiation of that membrane. All Turbellarians are built on 

 the same essential type, as regards muscular arrangement, as are 

 other worms. The general muscular arrangements in the bodies 

 of the Bijxdinm and JRhi/nchodemus ha\e become much modified 

 from those of flat Planarians by the pinching together and 

 condensation of the body ; but they are nevertheless referable to 

 the same t}'pe. 



The digestive tract consists of three tubes (one anterior, tA\o 

 posterior), as in other Planarians, and as in the embryo leech 

 before the formation of the anus. Characteristic of land-Planarians, 



