CTENOPHORES OF THE ATLANTIC COAST OF NORTH AMERICA 



late in ontogeny and grow outward from the sides of the 8 meridional 

 canals and may anastomose, thus producing a network connecting all 8 

 of the canals, and forming a complex circum-oral canal-system. This 

 remarkable similarity in respect to their canal-systems, together with 

 their marked compression in the funnel-axis, may, I think, be taken as 

 an indication that the Beroidae and Cestidas are related and derived 

 from a common stock. The condition exhibited by the fusion of the 

 paragastric and meridional systems of canals in the young Beroidae 

 and in mature Cestidae is shown in fig. 3, the lettering being similar in 

 purport to that of fig. 2. 



■nisv 



msr 



Fig. 3. — Diagram showing character of canal system in mature Cestidas 

 and young Beroidae. In the Beroidae the meridional and oral canals 

 finally give off side branches which may anastomose, and form circiim- 

 oral connectives, but these branches are not shown in the figure. 



We may classify the Ctenophorae in six orders as follows: 



I. Cydippid^:' Body spherical or cylindrical, or widest in the tentacular diameter. 

 Two long tentacles with or without side branches. The tentacles arise 

 from pit-like depressions in the sides of the body, which constitute sheaths 

 into which the tentacles may be withdrawn. The meridional and para- 

 gastric vessels do not fuse, but end blindly. No oral lobes, and no auricles. 

 il. Ganeshid^: Moser, 1907, Zool. Anzeiger, Bd. 31, p. 788; also, 1908, Revue 

 Suisse de Zool., tome 16, p. 12. 

 Body compressed in the tentacular axis. The oral forks of the 2 paragastric 

 canals form a complete ( ?) ring-canal around the mouth, and the 8 merid- 

 ional canals join this ring-canal. The interradial and tentacular canals 

 arise directly from the funnel. A tentacle-sheath is present. There are 

 no oral lobes and no auricles. The only known form is Ganesha elegans 

 Moser, from the Malay Archipelago. 

 This remarkable order appears to be intermediate in its general character 

 between the Cydippidag and Lobatas, but the fusion between the merid- 

 ional canals and the oral forks of the paragastric vessels recalls the condi- 

 tion seen in Cestidae and Beroidae. The Cestidae, however, lack a circum- 

 oral ring-canal, such as appears to exist in Ganes^ux. 

 III. LoBATiE: With 2 oral lobes in the stomodaeal axis and 4 ribbon-like projec- 

 tions (auricles), 2 from each tentacular side of the body above the mouth. 

 Body compressed in the funnel (tentacular) axis. The 4 subtentacular 

 meridional canals fuse with the ring-canal which the oral forks of the 2 

 paragastric canals form around the mouth. The 4 subventral meridional 

 canals fuse in pairs to form loops through the oral lobes, each canal 

 being connected with its fellow of the opposite side of the same oral 



