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 reéxamined 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, zpso 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 (Zerrebellides stremit), and 2 pelagic 
species, a mollusk, Janthina rotundata, and a copepod, Calanus 
finmarchicus; but even these last two hardly seem to be bipolar, 
since neither of them is recorded from further south than 35° 
S. L., and the latter seems to be rather a cosmopolitan form 
(see note on p. 340, oc. 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. 
