Chap, xii.] FLORA OF THE KERMADEC ISLANDS. 243 



of the great current which, stretching westward from the region 

 of Ducie, Pitcairn and Tubai Islands, follows the line of*the 

 Tropic of Capricorn, and branching, sends its northern half to 

 the east coast of Australia to form the East Australian current 

 whilst its other half passes down S.W. to sweep past the east 

 coast. 



The group lies just at the northern limit of the zone of 

 westerly winds, and within that of calms and changeable winds, 

 but so close to the limit that the winds may well have trans- 

 ported many of the plants, and the preponderance of ferns may 

 be due to the possible fact, that the winds have been the main 

 agents in the colonization of the islands, and have sufificed to 

 carry the minute fern spores, whilst heavier seeds have seldom 

 reached the island ; when they have done so it has been by 

 other means of transport. 



If fern spores are diffused mainly by wind, it should be 

 especially difficult for them to cross the zones of constant rains, 

 and there ought to be a marked separation of fern forms in 

 distribution about those lines. 



There is no connection between the flora of the Kermadecs 

 and that of Norfolk Island ; as Sir J. D. Hooker states, this 

 might have been expected, on general considerations. The 

 soundings of the "Gazelle" and "Tuscarora," have proved 

 that a channel of more than 2,000 fathoms in depth, passes up 

 between New Zealand and the Kermadec Islands. Hence, 

 an ancient land connection cannot be looked to as an explana- 

 tion of the New Zealand affinities of the Kermadec flora. 



Whilst dredging was going on off the islands, a shark {Car- 

 charias brachyiiriis), which was attended by a pilot fish {Mau- 

 crates sp.), was caught; it was, as is commonly the case, 

 covered by a small parasitic Crustacean, a species of Patidarus. 

 Some specimens of this parasite had, curiously enough, a 

 Barnacle {Lepas) attached to them as large as themselves. 



On the shark being skinned, I noticed that a layer of super- 

 ficial or skin muscles extending all over the animal, and only 

 about one-fourth of an inch in thickness, is coloured dark-red 

 by blood-colouring matter {Hemoglobin), as are all the muscles 

 of Mammalia. The main internal muscular mass of the shark 

 is pale, almost white. 



Prof. Ray Lankester has described several similar instances 

 of the restriction of the red colouring matter to certain muscles 

 only in animals which possess it.* A closely parallel case is 

 that of the little fish, the "Sea-Horse" {Hippocampus), in 

 which the muscles of the dorsal fin only are red. 



* E. Ray Lankester, "On the Distribution of Haemoglobin." Proc. 

 Royal Soc., No. 140, 1873. 



