32 EEPORT— 1886. 



Challenger Reports, in tlie Antarctic seas S. of 64° there is blue mud with 

 fragments of rock in depths of 1,200 to 2,000 fathoms. The stones, some' 

 of them glaciated, were granite, diorite, amphibolite, mica schist, gneiss, 

 and quartzite. This deposit ceases and gives place to Globigerina ooze 

 and red clay at 46° to 47° S., but even further north there is sometimes 

 as much as 49 per cent, of crystalline sand. In the Labrador current a 

 block of syenite weighing 490 lbs. was taken up from 1,340 fathoms, and 

 in the Arctic current 100 miles from land was a stony deposit, some stones 

 being glaciated. Among these were smoky quartz, quartzite, limestone, 

 dolomite, mica schist, and serpentine ; also particles of monoclinic and 

 triclinic felspar, hornblende, augite, magnetite, mica, and glauconite, the 

 latter no doubt formed in the sea-bottom, the others drifted from Bozoic 

 and Palaeozoic formations to the north.' 



A remarkable fact in this connection is that the great depths of the 

 sea are as impassable to the majority of marine animals as the land itself. 

 According to Murray, while twelve of the Challenger's dredgings taken 

 in depths greater than 2,000 fathoms gave 92 species, mostly new to 

 science, a similar number of dredgings in shallower water near the land 

 gave no less than 1,000 species. Hence arises another apparent paradox 

 relating to the distribution of organic beings. While at first sight it 

 might seem that the chances of wide distribution are exceptionally great 

 for marine species, this is not so. Except in the case of those which 

 enjoy a period of free locomotion when young, or are floating and pelagic, 

 the deep ocean sets bounds to their migrations. On the other hand the 

 spores of cryptogamic plants may be carried for vast distances by the 

 wind, and the growth of volcanic islands may effect connections which, 

 though only temporary, may afford opportunity for land animals and 

 plants to pass over. 



With reference to the transmission of living beings across the Atlantic, 

 we have before us the remarkable fact that from the Cambrian age on- 

 wards there were on the two sides of the ocean many species of inver- 

 tebrate animals which were either identical or so closely allied as to be 

 possibly varietal forms. ^ In like manner the early plants of the Upper 

 Silurian, Devonian, and Carboniferous present many identical species ; but 

 this identity becomes less marked in the vegetation of the more modei'n 

 times. Even in the latter, however, there are remarkable connections 

 between the floras of oceanic islands and the continents, which establish 

 this conclusively. Thus the Bermudas, altogether recent islands, have 

 been stocked by the agency chiefly of the ocean currents and of birds, 

 with nearly 160 species of continental plants, and the facts collected 

 by Helmsley as to the present facilities of transmission, along with the 

 evidence afforded by older oceanic islands which have been receiving 



■ General Rejyort, ' Challenger ' Expedition. 



2 See Davidson's Monographs on Brachiopods ; 'Etheridge., Address to Geological 

 Society of London; Woodward, Address to Geologists' Association; also Barrande's 



