Z CTENOPHORES OF THE ATLANTIC COAST OF NORTH AMERICA 



It will be seen that there are 2 1 ctenophores known from the Atlantic 

 coast of North America. Of these, 6 are cold-water forms and do not 

 commonly range southward of New Jersey along our coast, although 

 Arctic forms are sometimes driven, by winter storms, as far south as 

 Cape Hatteras; 3 are intermediate and are found between the south- 

 em shore of Cape Cod and northern Florida; 12 are tropical species, 

 some of which drift northward in summer to the region of Vineyard 

 Sound. Thus, along this whole stretch of coast, extending from the 

 Arctic regions to the tropics, we find only 21 species, while Chun records 

 20 from the Mediterranean. 



In no part of the North American coast are ctenophores as plen- 

 tiful or as numerous in species as in the Bay of Naples, where 17 

 kinds were found by Chun. In contrast to this, the Tortugas region, 

 which is richer in number of species than any other part of the North 

 American coast, has but 12 kinds of ctenophores. In the tropics, how- 

 ever, one does not often see the great swarms of one or a few species which 

 are so commonly met with in the cold or Arctic waters. At Newport, 

 Rhode Island, the surface of the sea is sometimes covered for thousands 

 of square yards with great submerged rafts of Mnemiopsis leidyi, the 

 individuals touching one the other, and the same phenomenon occurs 

 with Pleurobrachia pileiis or Bolinopsis infundibulum ofif the coast of 

 northern Maine. At Tortugas, Florida, on the contrary, dense swarms 

 of ctenophores are not seen, although more than twice as many species 

 are found in this tropical region than off the coast of Maine. 



Of the 21 forms described in this paper, 4 are new to science and 7 

 have not hitherto been recorded with certainty from the American coast ; 

 6 are Mediterranean species which extend across the tropical Atlantic 

 to the American coast. It is also of interest to see that 3 species, Pleu- 

 robrachia brunnea, Mnemiopsis leidyi, and M. gardeni are animals of the 

 temperate regions, never having been taken in Arctic or in tropical waters. 



A list of all of the then-known species of ctenophores with an account 

 of their geographical ranges is given by Moser, 1909, in Ctenophoren der 

 deutsch. Sudpolar-Expedition, Bd. 11, Zool. 3, p. 123. This important 

 paper also gives a very complete list of references to literature upon 

 ctenophores. 



It is unfortunate that the old and time-honored generic names Bo- 

 Una, Eucharis, Ocyroe, and Vexillum have been preoccupied and can not be 

 retained for Ctenophoras, and the names Bolinopsis, Leucothea, Ocyropsis, 

 and Folia are suggested to replace them. Much as I regret the change, 

 if the rules demand it we should make it at once. 



As is well known , the Ctenophorae are biradially symmetrical animals 

 with a slit-like mouth at one pole, and at the opposite end of the body 

 an apical sense-organ consisting of a mass of lithocysts said to be com- 

 posed of phosphate of lime, and inclosed in a capsule the walls of which 

 are probably formed of fused cilia, the mass of lithocysts being sup- 

 ported upon 4 flat triangular plates composed of fused cilia. On both 

 sides of the apical sense-organ there is a long, narrow, elevated ridge of 

 epithelial cells which are probably sensory and constitute the pole-plate. 



The mouth, which is at the opposite end of the body, is a long narrow 

 slit and leads into a laterally compressed chamber, the wide axis of which 



