HYDROMEDUSAE, SIPHON OPHORES, AND CTENOPHORES. 311 



tacles relative to canals. In short, we have here, as so often, a Di- 

 morphic Medusa with two fairly distinct types, with the great 

 majority of specimens belonging to one or the other. However, since 

 intermediates seem to be rare, the species macrodactylum may be re- 

 tained (1913, p. 37), until the normal range of variation is better 

 understood. 



Genus AEQUOREA Peron and Lesueur, 1809. 



AEQUOREA PENSILE (Haeckel) Mayer. 



Plate 42, figs. 3, 4. 

 Mesonema pensile Haeckel, 1879, p. 226. Synonymy, Mayer, 1910, p. 333. 

 Aequorea pensile — material examined. 



The decision as to whether this species should be called pensile or 

 coelum-p ensile (accepting Browne's idntification of it as Modeer's 

 Medusa coelum pensile) raises a nice question in nomenclature. 

 Most students, myself included, have called it pensile or pensilis 

 Modeer. But this position is untenable, because Modeer's name 

 (coelum pensile, adopted by Eschscholtz, 1829), was either a poly- 

 nomial, in which case, of course, it has no standing, or if he meant 

 it for a binomial, the two words coelum and pensile should be com- 

 pounded, as Vanhoffen (1913) has recently done. 



I have not had access to Modeer's papers. Least confusion will 

 result by following Browne and Mayer, and using pensile, but refer- 

 ring it to Haeckel on the ground that Modeer's name was a poly- 

 nomial. 



The specimens listed above agree with each other in having a very 

 large number of canals, in the entire absence of excretory papillae, 

 and in the fact that the tentacular bulbs never clasp the exumbrella. 

 Lateral extensions of these organs along the bell-margin, however, 

 are variable. In all the specimens from Limbones they are very 

 long, much as Browne (1905) has figured them; but in the example 

 50 mm. in diameter from station 5231 they are but slightly de- 

 veloped. The latter, however, is much contracted. Browne (1905) 

 has made a careful study of the margin. He finds, from serial sec- 

 tions, that excretory pores or slits are present, though the papillae 



