STRUCTURE AND nEVEUOPMENT OF COEUOrUANA. 9 



enclosed within a sheath and of the tentacle proper which can be stretched 

 out to such a lenj^th as may exceed twenty times that of the body 

 diameter. Besides, there exist "dorsal tentacles" (PI. 2, fig. i, PI. 2, fig. 

 4; d. t), which are the outgrowths of the gastro- vascular canals on the 

 dorsal side. Some ten to forty (commonly twenty to thirt}' in C. ivilleyi, 

 and ten to twenty in C. viitsiikurii and C. bocki) of them ma\' occur 

 in an individual, arranged along the course of the canals representing 

 the meridional canals of ordinary ctenophores. Their shape does not 

 differ in different species in the manner pointed out b\' Ai;iiOTT ('02, '07). 

 In all the species they may be said to be usually f)f a simple club-like, 

 and exceptionally of a divided or digitate, shape. 



As regards the mode of locomotin, Ar.iiOTT ('02, '07) has made 

 so full and correct a record that I have but little to add. The ventral 

 surface of the body appears to be highly thigmotrophic, as indicated by 

 the active manner in which the animal creeps right over a foreign object 

 it may come across during locomotion on a hard substratum or on the 

 surface of water, instead of avoiding it. 



P^reshly captured animals kept alive in a glass jar, are often seen 

 to discharge from the mouth pellets of about i mm. diameter. These 

 always prove to be undigested parts of the food taken, as well as some 

 other objects which happened to enter the mouth and consist generally 

 of some vegetable and animal matter agglutinated together by slime. 

 They usually contain diatoms in several forms, fragments of sea-weeds, 

 pieces of exoskeleton of small crustaceans, etc. Not infrequently even 

 small pieces of the tentacle of the animal were met with among the 

 ingredients. It was also observed that an empty but nearly perfect 

 skeleton of a certain isopod or amphipod was discharged from the mouth. 

 On this connection it may be mentioned that I have often come across 

 little pieces of striped muscles, apparently of some crustacean, imbedded 

 in the plasm of endodermal cells in the canal-system. Above observations 

 give an idea of what the animal subsists on. It seems after all that 

 Coeloplana takes nearly the same food as pelagic ctenophores or Tjalfiella 



(MORTENSEN, ' I 2). 



Anatomical and Histological Features. 



It will be convenient to give a brief account of the structure of 

 the body before entering into a detailed description of its parts. As 

 already mentioned, the body of Coelopla7ia is extremely changeable in 



