422 



NATURE 



[March 3, 1898, 



latitudes, is the great rarity or absence of the pelagic larvjs of 

 benthonic organisms, and in this respect they agree with similar 

 collections from the cold waters of the Arctic seas. The absence 

 of these larva; from polar waters may be accounted for by the 

 mode of development of benthonic animals to be referred 

 to presently. It must be remembered that many of these 

 pelagic organisms pass most of their lives in water of a 

 temperature below 32° F., and it would be most interesting.. to 

 learn more about their reproduction and general life-history. 



Benthos Life of the Antarctic Ocean. 



At present we have no information as to the shallow-water 

 fauna of the Antarctic continent ; but, judging from what we do 

 know of the off-lying Antarctic islands, there are relatively few 

 species in the shallov^ waters in depths less than 25 fathoms. 

 On the other hand, life in the deeper waters appears to be ex- 

 ceptionally abundant. The total number of species of Metazoa 

 collected by the Challenger 0.1 Kerguelen in depths less than 50 

 fathoms was about 130, and the number of additional species 

 known from other sources from the shallow waters of the same 

 island is 1 12, making altogether 242 species, or 30 species less 

 than the number obtained in eight deep hauls with the trawl 

 and dredge in the Kerguelen region of the,Southern Ocean, in 

 depths exceeding 1260 fathoms, in which eight hauls 272 .species 

 were obtained. Observations in other regions of t,he (ireat 

 Southern Ocean, where there is a low mean annual temperature, 

 also show that the marine fauna around the land in high 

 southern latitudes appears to be very poor in species down to a 

 depth of 25 fathoms, when compared with the nun^ber of species 

 present at the mud line about 100 fathoms, or even at depths of 

 about 2 miles. 



In 1 84 1 Sir James Ross stated that the animals he dredged 

 off the Antarctic continent were the sanjie as those he had 

 dredged from similar depths in the Arctic Seas, and he suggested 

 that they might have passed from the one pole to the other by 

 way of the cold waters of the deep sea. ^ Subsequent researches 

 have shown that, as with pelagic organisms, many of the 

 bottom-living species are identical with, or closely allied 

 to, those of the Arctic regions, and are not represented in 

 the intermediate tropical areas. For instance, the most striking 

 character of the shore- fish fauna of the Southern Ocean is 

 the reappearance of types inhabiting the corresponding lati- 

 tudes of the northern hemisphere, and not found in the inter- 

 vening tropical zone. This interruption of continuity in the 

 distribution of shore-fishes is exemplified by species as well as 

 genera, and Dr. Giinther enumerates eleven species and twenty- 

 nine genera as illustrating this method of distribution. The fol- 

 lowing are among the species : — Q\\\vc\-3tx2,.{Chinice.ra nionstrosa), 

 two species of Dog-fish (Acanthias vulgaris and A. Blainvilli), 

 the Monk-fish ( Khina squatina), John Dory (Zeus faber), Angler 

 {Lophius piscatorius). Bellows-fish [Centriscns scolopax), Sprat 

 (Clitpea sprat tus). The genus by which the family Berycidas is 

 represented in the southern temperate zone ( Trachichthys) is much 

 more nearly allied to the northern than to the tropical genera. ' ' As 

 in the northern temperate zone, so in the southern . . . the variety 

 of forms is much less than between the tropics. This is espe- 

 cially apparent on comparing the number of species constituting 

 a genus. In this zone, genera composed of more than ten species 

 are the exception, the majority having only from one to five." 

 ..." Polyfi'ion is one of those extraordinary instances in 

 which a very specialised form occurs at almost opposite points 

 of the globe, without having left a trace of its previous existence 

 in, or of its passage through, the intermediate space." 



Speaking of the shore-fishes of the Antarctic Ocean, Giinther 

 says : " The general character of the fauna of Magelhaen's Straits 

 and Kerguelen's Land is extremely similar to that of Iceland and 

 Greenland. As in the Arctic fauna, Chondropterygians are scarce, 

 and represented by Acanthias vulgaris and species of Raja. . . . 

 As to Acanthopterygians, Cataphracti, and Scorpsenidae are 

 represented as in the Arctic fauna, two of the genera [Sebastes 

 and Agonus) being identical. The Cottidse are replaced by six 

 genera of Trachinidse, remarkably similar in form to Arctic 

 types. . . . Gadoid fishes reappear, but are less developed ; as 

 usual they are accompanied by Myxine. The reappearance of 

 so specialised a genus as Lycodes is most remarkable."^ 



These statements with reference to shore-fishes might, with 

 some modifications, be repeated concerning the distribution and 

 character of all classes of marine invertebrates in high northern 



1 " Antarctic Voyage," p. 207. 



2 Giintiier, "Study of Fishes, pp. 282-290. 



NO. 1479, VOL. 57] 



(Edinburgh, 1880.) 



and high southern latitudes. The Challenger researches show 

 that nearly 250 species taken in high southern latituik-s' occur 

 also in the n.orthern hemisphere, but are not recorded - from the 

 tropical zone. Pifty-four species of sea-weeds have also been 

 recorded as showing a similar distribution.^ Bip61arity in the 

 distribution of marine organisms is a fact, however much 

 naturalists may differ as to its extent and the way in which it 

 has originated. 



All those animals which secrete large quantities of carbonate 

 of lime greatly predominate in the tropics, siich as Corals, 

 Decapod Crustacea, Lamellibranchs, and Gasteropods. On the 

 other hand, those animals in which there is a feeble develop- 

 ment of carbonate of lime structures predominate in cold polar 

 waters, such as Hydroida, Holothuroidea, Annelida, Amphi- 

 poda, Isopoda, and Tunicata. This difference is in direct rela- 

 tion with the temperature of the water in which these organisms 

 live, carbonate of lime being thrown down much more rapidly 

 and abundantly in warm than in cold water by ammonium 

 carbonate, one of the waste products of organic activity. 



In the Southern and Sub-antarctic Ocean a large proportion 

 of the Echinodernis develop their young after a fashion which 

 precludes the possibility of a pelagic larval stage. The young 

 are reared within or upon the body of the parent, and have a 

 kind of commensal connection with her till they are large 

 enough to take care of themselves. A similar method of direct 

 development has been observed in eight or nine species of 

 Echinoderms from the cold waters of the rtorthern hemisphere; 

 On the other hand, in terhperate and tropical regions, the de- 

 velopment of a free-swimriiing larva is so entirely the rule that it 

 is usually described as the normal habit of the Echinodermata. 

 This similarity in the mode of development between Arctic arid 

 Antarctic Echinoderms (and the contrast to what takes place in 

 the tropics) holds good also in other classes of Invertebrates, 

 and probably accounts for the absence of free-swimming larvae 

 of benthonic animals in the surface gatherings in Arctic and 

 Antarctic waters. • . 



What is urgently required with reference to the biological 

 problems here indicated is a fuller knowledge of the facts, and 

 it cannot be doubted that an Antarctic expedition would bring 

 back collections and observations of the greatest interest to all 

 naturalists and physiologists, and without such information it is 

 impossible to discuss with success the present distribution of 

 organisms over the surface of the globe, or to form a true con- 

 ception of the antecedent conditions by which that distribution 

 has been brought about. 



Concluding Remarks. 



There are many directions in which an Antarctic Expedition 

 would carry out important observations besides those already 

 touched on in the foregoing statement. From the purely 

 exploratory point of view much might be urged in favour of an 

 Antarctic Expedition at an early date ; for the further progress 

 of scientific geography it is essential to have a more exact know- 

 ledge of the topography of the Antarctic regions. This would 

 enable a more just conception of the volume relations of land 

 and sea to be formed, and in connection with pendulum observ- 

 ations some hints as to the density of the sub-oceanic crust and 

 the depth of the Antarctic ice- cap might be obtained. Incase 

 the above sketch may possibly have created the impression 

 that we really know a great deal about the Antarctic regions, 

 it is necessary to re-state that all the general conclusions that 

 have been indicated are largely hypothetical, and to again urge 

 the necessity for a wider and more solid base for generalisa- 

 tions. The results of a successful Antarctic Expedition would 

 mark a great advance in the philosophy— apart from the mere 

 facts — of terrestrial science. 



No thinking person doubts that the Antarctic will be explored. 

 The only questions are : when? and by whom? I should like 

 to see the work undertaken at once, and by the British Navy. 

 I should like to see a sum of 150,000/. inserted in the estimates 

 for the purpose. The Government may have sufficient grounds 

 for declining to send forth such an expedition at the present 

 time, but that is no reason why the scientific men of the country 

 should not urge that the exploration of the Antarctic would 

 lead to important additions to knowledge, and that, in the 

 interests of science among English-speaking peoples, the United 

 Kingdom should take not only a large but a leading part in any 

 such exploration, 



1 Murray and Barton, " Phycological Memoirs of the British Museum," 

 Part 3. (London, 1895.) 



