9O Comparison of the Arctic and Antarctic Marine Floras. 



and Campbell's Islands, from which we have records by Hooker and 

 Harvey (Antarctic Voyage], by Dickie, in the Challenger and Transit 

 of Venus (Kerguelen) Expeditions, and by Harlot in the Mission 

 Scientifique du Cap Horn. From these sources the list has been 

 compiled, and brought under the same system of classification as that 

 adopted by Kjellman ; and, of course, it has been tested by our 

 knowledge of the material. 



It will be seen from the totals that the number of species in the two 

 floras is fairly even, viz., 259 in the Arctic and 269 in the Antarctic. The 

 Arctic species are in 1 1 1 genera, i.e., an average of 2\ species to the genus 

 exactly. The Antarctic species are in 98 genera, i.e., very nearly an average 

 of 2f species to the genus. The average proportion of species to genera 

 in other seas has been commented on before (p. 66). The genera 

 common to both oceans is 56, and the species 41. But no less than 

 42 of the species here recorded as Antarctic, and not Arctic, occur in 

 the north temperate zone. This probably means, in part, that we have 

 drawn our Antarctic line too near the south temperate ocean. Similarly, 

 on comparing the Arctic list with Miss Barton's Cape of Good Hope 

 list, we find another 9 species occurring in both, but not recorded from 

 the Antarctic. Adding these figures together, we get 92 species common 

 to northern and southern polar and partly temperate coasts. Of these, 

 however, 38 species occur in the intervening Tropics are cosmopolitan, 

 in short, and we must subtract them from the above total, yielding 54 

 species in common north and south of the tropical belt, and not occurring 

 within it. Out of the two totals of 259 and 269 there are thus 54 

 species in common which have not been found within the Tropics. If 

 we were to compare all the north temperate and south temperate 

 littoral seaweeds (instead of the polar forms mixed with certain 

 temperate forms that enter polar seas at either pole as we have done), 

 we should run a greater risk of counting species as extra-tropical, 

 which are probably really tropical though not recorded. Therefore it 

 appears to us to be a more safe proceeding to deal only with polar 

 and adjoining waters. 



The tables disclose a number of interesting facts in distribution, the 

 principal one being this, that all the genera in the list of Fucacece and 

 LaminariacetZ) the largest seaweeds, are either Arctic or Antarctic none 

 of them are both. Some of these genera, e.g., Macrocystis, Laminaria, 

 are found, however, on both sides of the tropical belt, and other genera 

 not mentioned here, e.g., PycnopJiycus (Fucacecz} occur in both temperate 

 belts, but all such occurrences are exceptional among the great seaweeds. 

 Nothing, in fact, is more striking in the distribution of seaweeds than the 



