18 CTENOPHORES OF THE ATLANTIC COAST OF NORTH AMERICA 



meridional vessels are wide and their edges exhibit a wavy outline, prob- 

 ably due to contraction. The 2 paragastric vessels are well developed and 

 closely pressed to the sides of the stomodaeum. They flare outward at 

 the level of the mouth. The 2 tentacular canals are very short and the 

 tentacle bases small, but the sheaths are correspondingly long and extend 

 downward and finally outward, to open very near the mouth at about 

 the level of the oral ends of the meridional canals. I have never seen 

 the tentacles protrude beyond the sheaths, but they appear to have 

 lateral filaments. 



I have not seen the genital products and can not state that the 

 specimens were mature, for the dull milky color of this animal renders 

 it only about as translucent as ground glass, so that minute details of 

 its internal structure can be seen only with difficulty. It is rare and I 

 have seen only 4 specimens between May and July at Tortugas, Florida. 

 It comes to the surface only when the water has been calm and unrippled 

 for some hours. 



Order LOBAT^ L. Agassiz, i860. 



BeroidcB lobatcB, Eschscholtz, 1825, Isis, p. 741. 



MnemiidcB, Eschscholtz, 1829, Syst. der Acal., p. 29. 



CallianiridcB, Mertens, 1833, M^m. Acad. St. P6tersbourg, sir. 6, tome 2, p. 495. 



CalymmidcB, Gegenbaur, 1856, Archiv ftir Naturges., Jahrg. 22, p. 192. 



Lobatcs, Agassiz, L., i860. Cont. Nat. Hist. U. S., vol. 3. pp. 199, 289. — ^Agassiz, 

 A., 1865, North Amer. Acal., p. 14. — Chun, 1880, Ctenophoren Golfes von 

 Neapel, p. 287, 1898, Ctenophoren der Plankton-Expedition, p. 22. — Van- 

 hOffen, 1906, Nordisches Plankton, Ctenophoren, p. 4. — Moser, 1903, Cteno- 

 phoren der Plankton-Expedition, p. 16; also, 1908, Abhandl. Akad. Miinchen, 

 Suppl. Bd. I, Abhandl. 4, p. 36; also i, 1909, Ctenophoren der deutsche S<id- 

 polar-Exped., Bd. 11, Zool. 3, p. 161. 



CHARACTERS OF THE LOBAT^. 



The body is laterally compressed, the gastric axis through the stomo- 

 daeum and oral lobes being longer than the funnel-axis through the lateral 

 tentacles. There are 2 oral lobes, i on each side of the mouth. At the 

 lower ends of each of the subtentacular combs of cilia there are 4 freely 

 projecting, ribbon-like auricles which are fringed along their narrow 

 edges with cilia. The 4 principal, interradial, entodermal canals spring 

 directly from the funnel. The meridional canal-system communicates 

 with the X-shaped oral ends of the 2 paragastric tubes and also winds 

 in a more or less complex manner in the substance of the oral lobes. 

 The tentacle bases are near the oral pole. There are no tentacle-sheaths. 



The larva passes through a Mertensia-like stage, and in Leucothea 

 the animal may become sexually mature while in this condition. 



It is evident that the Lobatas are derived from the Cydippidae and 

 that they came from Mertensia-like ancestors. 



It is interesting also to see that the Cestidae are closely related to 

 the Lobatas, and the canal-systems of the Cestidae and Beroidae are som-c- 

 what similar each to each in their general features. 



