PRESIDENT'S ADDRESS. 169 
to the existence of the similarity and as to its explanation. 
In-2 recent summary of the evidence in favour of the theory, 
Mise E. M. Pratt (Pratt, 01) says that Pfeffer, Murray, 
Selenka, De Guerne, Fischer, Shipley, Théel, Ehlers, I. C. 
Thompson, and herself, who have all worked on material 
from the far South, are believersinthe resemblances. Onthe 
other side, we have D‘Arcy Thompson, Herdman, Ludwig, 
Chun, and Ortmann, who also speak from personal know- 
ledge, and are just as strong in their disbelief of the simi- 
larity of the two faunas. 
The evidence marshalled by the supporters of the idea asto 
the present distribution of the fauna is explicit, and must 
be weighed and valued by expeiis in the various groups; 
but there seems to be no doubt ihat there are certain 
animals—-either species or genera, or even higher groups— 
which are present in both Arctic and Aniarctic seas, and 
appear to be absent from the intervening ones. Even if 
there. be no specific agreement in the case, still the 
resetrnblances in some cases are undoubted. But even if we 
take the statements as te the great similarity of the two 
polar faunas as correct, we have yet to consider the theory 
which would explain the asserted facts. 
Sir John Murray (Murray, ’95) gives a laborious summary 
of the question. Taking the Kerguelen region as typical, 
he finds about 530 animals are known. Of these 45 occur 
in the North Atlantic. 11 in the North Pacific, but only 18 
in the tropical Atlantic, and 22 in the tropical Pacific. He 
concludes that it may “ be assumed that the identical species 
now found living towards both poles, or their immediate 
ancestors, had a world-wide distribution, which involves a 
nearly uniform temperature throughout the whole body of 
ocean waters.” iS 
Perhaps the most trenchant article against the theory is 
that of D’Arcy Thompson (Thompson, ‘00), in which he dis- 
cusses Murray’ list in detail, and sums up by saying (I.c., p. 
313)—“ Many, if not most [of these] , are dubious, even in 
the eyes of their first recorders—many others have too fow 
characters for precise recognition.’’ He also ingists, with 
justice, as we shall see in the sequel, that we must “dis 
criminate between those whose affinities appertain to the 
farma of the North Pacific and of the North Atlantic res 
pectively. For the fauna of the North Pacific presents 
many unknown problems for us; but this we do know, that 
it contains in paré a northern circumpolar fauna, and in part 
a fauna very distinct from that of the North Atlantic, and 
peculiarly linked to the fauna cf the Southern Qcean.” 
