516 



SCIENCE. 



[N. S. Vol. VIII. No. 198. 



However, if the specialists in any group can 

 permanently agree among themselves in the 

 designation of the types of genera now recog- 

 nized, there is no reason why any changes need 

 be made. No new difBculties are, indeed, in- 

 troduced by these suggestions ; but to carry 

 them out would simply bring to definite ex- 

 pression the disagreement and confusion latent 

 among systematists, and make plainer the fact 

 that uniformity and stability stand in inverse 

 ratio to the personal equation ; which means 

 that some uniform, and hence arbitrary, method 

 ■of assigning types for fixing the application of 

 the older generic names will probably be neces- 

 sary, such as the use of the first designated 

 species. O. F. Cook. 



U. S. National Museum, 

 September 22, 1898. 



THE SUPPOSED BIPOLARITY OP POLAE FAUNAS. 



Dr. John Murray, in a recent paper,* again 

 mentions the supposed general likeness of a 

 large number of organismsca ptured in the Ant- 

 arctic seas to those found in the Arctic seas (p. 

 133). I should like to say a few words on this 

 topic, since I have paid particular attention to 

 this question, and have repeatedly endeavored 

 to show that in most cases this supposed ' bipo- 

 larity ' does not exist at all, while in others it is 

 no true bipolarity, cases of true bipolarity be- 

 ing extremely rare. 



Especially for the Decapod Crustaceans I have 

 found that "not a single bipolar species is 

 known. "f This sentence is quoted by Dr. 

 Murray (1. c), and he tries to show its incor- 

 rectness by mentioning the close resemblance 

 of Lithodes murrayi Hend. of the Kerguelen 

 region to Lithodes maja (L.) from the North- At- 

 lantic, and by adding that — according to a 

 communication by Mr. Henderson — there is no 

 better illustration of bipolarity than that fur- 

 nished by the Lithodidee. 



I cannot admit these objections, since they 

 are not supported by the facts. We possess a 

 very valuable monograph of the Lithodidse pub- 



*0n the annual range of temperature in the surface 

 waters of the Ocean and its relation to other Ooeano- 

 graphioal phenomena. Tlie Geographical Journal, 

 August, 1898, v., 12, No. 2. 



tZool. Jahrb. Syst., v. 9, 1896, p. 585. 



lished by Mr. E. L. Bouvier in 1896,* and Mr. 

 Bouvier has shown plainly — as I have main- 

 tained previously — that the chief distribution 

 of the Lithodidse is what I have called meridional 

 distribution ; that is to say, a distribution in the 

 direction North-South, along the western coasts 

 of the continents. It is a true case of false or 

 mistaken bipolarity, a connection of the Arctic 

 and Anarctic range of this family being present 

 along the western coast of America (and per- 

 haps of Africa). Moreover, according to the 

 key of species and the notes given by Mr. Bou- 

 vier (1. c. p. 24), Lithodes maja is not at all the 

 most closely allied form to L. murrayi ; but 

 there are two other species which may claim 

 this distinction, namely : L. tropicalis A. M. E. 

 and L. ferox A. M. E., both from tropical lati- 

 tudes off the western coast of Africa, where 

 they have been found in depths ranging from 

 800 to 1100 meters. This fact again suggests a 

 connection from the Arctic to the Antarctic seas 

 along the western coast of Africa, and we see 

 that true bipolarity in the family Lithodidse as 

 well as in the genus Lithodes is wholly out of 

 the question. 



I cannot understand at all why Dr. Murray 

 again and again calls attention to the supposed 

 bipolarity of the polar faunas as a striking fea- 

 ture in zoogeography. Most of the cases intro- 

 duced formerly as instances illustrating this 

 bipolarity could not be maintained after a crit- 

 ical examination of the respective zoogeograph- 

 ical facts. Thus, among the Decapods this 

 theory finds no support, as I have shown, and 

 likewise the supposed bipolarity of the Holo- 

 thurians (Th6el) does not exist, since Professor 

 H. Ludwigf states that ' ' not a single species of 

 the Antarctic fauna is represented in the Arctic 

 fauna," and that " there is not even a resem- 

 blance of both faunas, but a great dissimi- 

 larity. ' ' 



Thus we see that a critical examination les- 

 sens the number of the superficially recorded 

 cases of bipolarity, and that my doubts as to 

 the correctness of the bipolarity as a prime law 

 or as a striking feature of distribution are fully 

 supported, and I am convinced that a careful 



*Ann. Soi. Nat. Zool. (8) v. 1. 

 t Hamburger Magalhaensisohe Sammelreise. Holo- 

 thuriden, 1898, p. 90, f. 



