KUNGL. SV. VET. AKADEMIENS HANDLINGAR. BAND 47. NIO I. 5 



for estimating tho nature of the phenomenon of bipolarity. This concerns especiallj 

 forms which like the species of Priapulus ha ve attained such an unusually high degree 

 of speciality, tliat all eonvergence-phcnomena due to variation and similar physical 

 conditions are excluded. If, in addition, it be proved that the anirnals in question 

 neither in adult nor in laval stages are capable of moving from polar cirole to polar 

 circle and, besides, that they do not exist in intermediate zones, then \ve are entil Led 

 to tura to every scientific man with the question: What is the reason for such a 

 conspicuous resemblance? For science cannot allow that two exactly identical forms 

 have arisen from two sources only by means of variations and similar physical con- 

 ditions. 



Supposing such views were right, then, indeed, the relationship between the 

 organisms would be veiled in a mystery much more chaotic than before Darwin. 

 Therefore it is our duty to try to find a true interpretation of such a very remarkable 

 phenomenon as that of the true bipolarity. Moreover, according to my opinion, the 

 obvious resemblance and the general features of the faunas of the two polar seas 

 must remain mysterious, if we do not admit a closer relationship. It cannot be 

 explained by convergence phenomena alone. 



In many instances, it is true, a certain resemblance between the two polar 

 faunas may be explained solely by »variation and evolution under similar conditions», 

 but surely there exist resemblances so intimate, that they are incomprehensible without 

 assumption of a close relationship. 



As early as in 1886, l when worlcing with the Challenger Holothurids, I suggested 

 the following views: »It appears scarcely probable that the shore-fauna of two regions so 

 far separated from each other as the arctic and antartic seas, has any direet exchange 

 of forms at the present epoch, so as to allow the same species, in its larval or adult 

 state, to pass from one pole to the opposit without settling at interjacent regions. In 

 brief, I do not believe that at the present epoch the arctic shallow water fauna can directly 

 originate from the antarctic, or vice versa.». . . »On the other hand, it is a fact that the 

 two faunas in question resemble each other very closely, and, with regard to the Holo- 

 thurids, that several forms occur in the arctic sea which are most closely allied to those 

 in the antarctic. I am inclined to suppose that the progenitors of the Holothurids have 

 had a much wider distribution during a past period, that altered physical conditions, a 

 keener struggle for existence etc, under the tropic and the temperate zones have effected 

 their extinction, or their migration towards the polar seas, or even produced changes in 

 their organisation and general appearance so marked, that their descendants which still 

 remain in the tropical zones present themselves as species distinct from the original, and 

 finally that the polar seas with their more uniform physical conditions alloiced tlxem and 

 their descendants to tive their and to develop slowly but continuously after almost the 

 same plan.» 



Ever since that time I have had no ground for changing my views to any 

 particular extent: for, according to my opinion, it is inconceivable that the shallow - 



1 Challenger Report. Zoology. Vol. XIV. Part XXXIX, p. 260; and Ymer, tidskrift utgifven af säll- 

 skapet för Antropologi och Geografi. Stockholm 1900. 3. 



