JlL> ZOOLOGY SECT 



APPENDIX TO CTENOPHORA 



CTKNOPLANA AND C<KL<>PLANA. 



Before leaving the Ctenophora mention must be made of two remarkal)le 

 organisms which have been supposed to connect the present class with the 

 Turbellaria Polycladida, or Planarians, a group of worms to be described in 

 the following section. 



Cttuoplaim (Fig. 159) is a small marine animal, nearly circular in outline, 

 flattened dorso-ventrally, and about 6 mm. in diameter. It has hitherto been 

 found only twice once in the Indian Ocean and once in New Britain. Instead 

 of swimming freely, like a Ctenophoran, it creeps on its ventral surface, like 

 a worm. In the centre of the dorsal surface is a vesicle (.s\o.) containing 

 an otolith surrounded by eight radiating ridges (r.r.), alternating with which 

 are as many clefts (cL ), each containing a protrusible row of stiff processes, 



5 G 



A 



B 



Vic,. 1 :>.>. Ctenoplana kOwalevskii. A, from above, B, from the side. cL clefts; r. r. 



radiating ridges ; *. /. sen.se-org;in. (After Korotneff.) 



resembling the swimming-plates of Ctenophora. The mouth is in the centre 

 of the ventral surface, and leads into a stomach, from which are given off 

 numerous anastomosing canals, as well as a vertical canal which passes upwards 

 and ends beneath the sense-organ. In diverticula of this system are formed the 

 testes, which have independent ducts opening on the exterior. There are two 

 solid tentacles contained in sacs, and a nerve-centre lies beneath the sense-organ 

 (x.o. ). Beneath the ectoderm is a basement-membrane, which acts as an organ 

 of support, and the muscular system is complex. Xear each tentacle is an 

 aperture leading into a branched canal which is probably excretory, like the 

 nephridial tubes of flat-worms. 



< '<,-l<>/,l(iiiri, is found in the Red Sea. It is also flattened dorso-ventrally, but 

 is oval instead of circular in outline, its dimensions being about 6 by 4 mm. It 

 resembles Ctenoplana in its ventral mouth, dorsal sense-organs, paired retractile 

 tentacles, and complex system of anastomosing canals from the stomach. There 

 are, however, no swimming-pistes, and the ectoderm is ciliated. 



Nothing is known of the development of either genus, 



