ANIMAL LIFE IN THE OCEAN. 651 



" This expectation was most remarkably confirmed by the Challenger 

 researches ; one of the most important of the general results of that ex- 

 pedition being the recognition of an abyssal Fauna, essentially the same, 

 over the whole oceanic area that is reached by the glacial underflow, 

 without any relation whatever to the terrestrial climate of the locality, 

 and scarcely showing any difference according to its Arctic or Antarctic 

 derivation. Thus we see that, even at the present time, the essential 

 conditions of a " glacial epoch " prevail upon the Deep- Sea bed from each 

 Pole to the Equator ; so that the presence of Arctic types of animal life 

 in any marine deposit of Temperate or even Tropical zones, affords not 

 the least evidence, per se, of the former extension of glacial action over 

 the land of these localities." 



Sir Wyville Thomson remarks :* — " The most prominent and remarkable 

 biological result of the most recent investigations is the finaPestablish- 

 ment of the fact that the distribution of living beings has no depth limit ; 

 but that animals of all the marine invertebrate classes, and probably 

 fishes also, exist over the whole of the floor of the ocean. My present 

 impression is, that, although life is thus universally extended, the number 

 of species and of individuals diminishes after a certain depth is reached, 

 and that at the same time their size usually decreases. 



" Using all precautions and with ample power and the most complete 

 apphances.f it is extremely difficult to work either with the Dredge or 

 with the Trawl at depths approaching or exceeding 3,000 fathoms. A 

 single dredging operation in such depths takes a long time; the Dredge is 

 put over at daybreak (the ship being kept as nearly as possible stationary), 

 and it is usually dark before it is recovered, so that the number of such 

 operations must be comparatively small. We must therefore bear in 

 mind that only an infinitesimally small portion of the floor of the Ocean, 

 at depths over 2,500 fathoms, has yet been explored. 



" As we had previously anticipated, the Fauna at great depths was 

 found to be remarkably uniform. Species nearly allied to those found in 

 shallow water, of many familiar genera, were taken in the deepest hauls, 

 BO it would seem that the enormous pressure, the utter darkness, and 



• " Voyage of the Challenger; the Atlantic," vol. ii. 



t In the examination of the Animal Life, three forms of apparatus were used by 

 H.M.S. Challenger. 1. A Dredge, consisting of a dredge-bag attached to an iron frame 

 4^ ft. long by 1^ ft. broad. To the bottom of the frame was attached a bar, bearing 

 tangles of rope-yarn, in order to entrap various animals while passing over the bottom. 

 The dredge-bag usually came up from the bottom, at great depths, full of mud [glvbi- 

 gerina ooze, ^c), but on one occasion a huge block of syenite was brought up in the 

 mouth of the dredge from a depth of 1,340 fathoms, about 160 miles southward of Cape 

 Sable in the North Atlantic. 2. The Deep-Sea Trawl, a conical bag 3C ft. in length, 

 \7eighted at its bottom end, and suspended by one side of its mouth to a beam of wood; 

 ♦he other side of the mouth, which drags along the sea-bottom, hangs loose, and in 

 order that the bag may keep open is weighted with some pieces of lead. The mouth 

 of the Trawl-bag is fitted with a netted funnel arrangement which prevents the escape 

 of animals after capture. 3. An ordinary Trawl-net, kept open at its mouth by an iron 

 ring, was dragged behind the vessel at small depths. The accumulators (page 923), to 

 which the dredge-ropes were attached, were slung from the mainyard-arm, aud the 

 hauling in cf the dredges was eOcctod by a donkey-engine. 



