No. 391.] BIPOLARITY OF MARINE FAUNAS. 587 



to or modified in such a way as to entirely change the nature 

 of their evidence, and show that there is no such close resem- 

 blance between the northern and southern polar faunas as 

 Dr. Murray and others have supposed." In fact, he states 

 plainly that among the simple ascidians no cases of bipolarity 

 are known. 



D'Arcy W. Thompson * has reexamined the list of bipolar 

 animals given by J. Murray. This list contains nearly 100 

 species, but d'Arcy W. Thompson shows (p. 347) that there 

 are among them " more than one-third in which grave doubt as 

 to their identification was expressed by the original describers, 

 or in which the identification has been doubted or denied by 

 later writers. In somewhat more than another third the evi- 

 dence of identity is inconclusive or even inadmissible by reason 

 of the nature of the examination to which the specimens were 

 subjected, or by reason of the small size of the objects and lack 

 of adequate marks of characterization. Of the remaining forms, 

 about a dozen find their northern representatives in the Japanese 

 seas, where they form part of a fauna predominantly southern 

 in its relations, and where at least the occurrence of any par- 

 ticular form cannot be taken, ipso facto, as evidence of a boreal 

 center of distribution." 



After deducting these forms the list shrinks into very little. 

 There remains, aside from 12 deep-sea species, only a single 

 littoral annelid species (Terre be ilides strcemii), and 2 pelagic 

 species, a mollusk, Janthina rohindata, and a copepod, Calanns 

 finmarchicus ; but even these last two hardly seem to be bipolar, 

 since neither of them is recorded from further south than 35 o 

 S. L., and the latter seems to be rather a cosmopolitan form 

 (see note on p. 349, loc. cit.). 



Further, d'Arcy W. Thompson gives an examination of the 

 Antarctic fishes, isopods, and amphipods, with special reference 

 to bipolarity. He finds no species in any of these groups to 

 inhabit both the Arctic and Antarctic Oceans, and he sees no 

 signs of a likeness of both faunas. 



A valuable series of monographs has been published by 



1 On a Supposed Resemblance between the Marine Faunas of the Arctic and 

 Antarctic Regions, Proc. Roy. Soc. Edinburgh (1898), pp. 311-349. 



