374 bulletin: museum of comparative zoology. 



I have seen, the funnel is at least no longer than the oesophagus, and 

 the canal junction lies on a level with, or slightly above the funnel. 

 Apart from these features comparison, side by side, of considerable 

 series has failed to reveal a single difference between the Atlantic 

 and Pacific forms. 



Moser ( : 09) has pointed out that pileus is extremely variable in 

 form and proportions, both individually and with different stages in 

 growth, a conclusion which my own observations substantiate; and 

 the "bachei" type may well lie within the normal limits of variation 

 of pileus, as Moser supposes, though I can not prove this as a first 

 hand observation. Nevertheless the fact remains that all the Pleuro- 

 brachias of the pileus type yet recorded from the west coast of North 

 America belong to a variety which is certainly not the prevailing one 

 in the north Atlantic, although it may occur there. But the " bachei" 

 form is apparently not generally distributed over the Pacific as a whole, 

 for it is known only from the west coast between lat. about 49° N. and 

 about 17° N.; and the Pleurobrachia record from New Zealand, 

 is typical pileus, as are the records from the Seychelles, from South 

 Africa, and from the Antarctic (Moser, : 09) . 



Moser thinks it probable that the Pleurobrachias of the west coast 

 of North America are carried thence by the cold "Polarstrom, " 

 and the "globular Ctenophore" mentioned by Chamberlain (:06) 

 as common off the Alaskan coast is probably a Pleurobrachia, as is 

 the " Beroe octoptera" of Mertens ('33) from Behring Straits. But 

 to show how scanty our knowledge in this field is, I would point out 

 that there is not another record of the genus from either side of the 

 Pacific north of Puget Sound. Furthermore, I find no Pleurobrachias 

 in all the extensive collections which have been gathered by the 

 "Albatross" in the northwestern Pacific, though her voyages in that 

 region have extended along the entire coast of Alaska, Behring Sea, 

 the Aleutian Islands, and Japan, and, from year to year, have been 

 prosecuted in every month from May to October. 



In the meantime, however, some disposition must be made of the 

 Californian Pleurobrachia in our system of classification. Decidedly 

 it is not a distinct species. But on the other hand to unite bachei 

 unreservedly with pileus, of which it is undoubtedly a component, 

 will only hide the need of further investigation. Among the higher 

 vertebrates the solution would be a subspecies, but inasmuch as 

 this rank is not recognized among Ctenophores, Medusae, or Siphon- 

 ophores, the most satisfactory way is to consider the form, for the time 

 being, a variety. 



