September 5, 1S84.] 



SCIENCE. 



211 



cies, which range even from the shore-region to great 

 depths. These facts add seriously to the difficulties 

 encountered in the attempt to determine approxi- 

 mately the depths at which geological deposits have 

 been found. Dr. Theodore Fuchs has attempted to 

 determine what geological strata should be considered 

 as of deep-sea formation; but, as he defines the deep- 

 sea fauna as commencing at a hundred fathoms, and 

 extending downwards to all depths, his results have 

 little value as indicating the depths of ancient seas, or 

 the extent of upheaval or depression of their bot- 

 toms. Mr. John Murray has shown that the depths 

 at which modern deep-sea deposits have been formed 

 can be approximately ascertained by the examination 

 of their microscopical composition, and the condition 

 of preservation of the shells and spicules. 



The most important question with regard to life in 

 the ocean, at present insufficiently answered, is that 

 as to the conditions with regard to life of the inter- 

 mediate waters between the surface and the bottom. 

 The greatest uncertainty and difference of opinion 

 exist as to whether the intermediate waters are 

 inhabited at all by animals, and, if they are inhab- 

 ited, to what extent; and these intermediate waters 

 constitute by far the greater part of the ocean. 

 Great care should be exercised in drawing conclu- 

 sions from the depths ascribed to animals in some of 

 the memoirs in the official work on the Challenger 

 expedition. In many instances it is quite possible 

 that a particular specimen may have entered the 

 net at any depth. 



With regard to the constitution of the deep-sea 

 fauna, one of its most remarkable features is the gen- 

 eral absence from it of paleozoic forms, excepting so 

 far as representatives of the Mollusca and Brachiopo- 

 da are concerned ; and it is remarkable, that, amongst 

 the deep-sea Mollusca, no representatives of the Nau- 

 tilidae and Ammonitidae, so excessively abundant in 

 ancient periods, occur, and that Lingula, the most 

 ancient brachiopod, should occur in shallow water 

 only. It might well have been expected, that, had 

 the deep sea been fully colonized in the paleozoic 

 period, a considerable series of representative forms 

 of that age might have survived there, in the absence 

 of most of the active physical agents of modification 

 which characterize the coast-regions. 



With regard to the origin of the deep-sea fauna, 

 there can be little doubt that it has been derived 

 almost entirely from the littoral fauna, which also 

 must have preceded, and possibly given rise to, the 

 entire terrestrial fauna; yet it is not improbable that 

 we should look to the pelagic conditions of existence 

 as those under which most of the earliest types of 

 animal life were developed. Nearly all the present 

 inhabitants of the littoral zone revert to the pelagic 

 free-swimming form of existence in their early devel- 

 opmental stages. And these pelagic larval forms are 

 in many cases so closely alike in essential structure, 

 though springing from parents widely differentiated 

 from one another in the adult form, that it is impos- 

 sible to regard them as otherwise than ancestral. 

 The various early pelagic free-swimming forms, rep- 

 resented now mostly only by larvae, gradually adapted 



themselves to coast-life, and underwent various modi- 

 fications to enable them to withstand the beating of 

 the surf on the shores, and the actual modifying al- 

 terations of the tides, which, together with other cir- 

 cumstances of coast-life, acted as strong impulses to 

 their further development and differentiation. Some 

 developed hard shells and skeletons as protections; 

 others secured their position by boring in the rocks 

 or mud ; others assumed an attached condition, and 

 thus resisted the wash of the waves. 



It is because the ancestors of nearly all animals 

 have passed through a littoral phase of existence, 

 preceded mostly by a pelagic phase, that the investi- 

 gations now being carried on, on the coasts in marine 

 laboratories, throw floods of light on all the funda- 

 mental problems of zoology. From the littoral fauna 

 a gradual migration must have taken place into the 

 deep sea; but probably this did not occur till the lit- 

 toral fauna was very fully established, and consider- 

 able pressure was brought to bear on it by the 

 struggle for existence. Life, too, must have become 

 abundant in the littoral zone before there could have 

 been a sufficient food-supply in the deeper regions 

 adjoining it. Not until the development of terres- 

 trial vegetation and animal life can the supply have 

 reached its present abundance. Such a condition 

 was, however, certainly reached in the carboniferous 

 period. From the general absence of representatives 

 of paleozoic forms from the deep sea, it is just pos- 

 sible, that, if deep oceans existed in paleozoic periods, 

 they may not have been colonized at all, and that 

 active migration into deep waters commenced in the 

 secondary period. Very possibly the discharges of 

 carbonic acid from the interior of the earth, which 

 Professor Dittmar believes may have been sufficient 

 to account for the vast existing deposits of coal and 

 limestone, may have been much more abundant over 

 the deep-sea beds in the paleozoic period, than at 

 present, and have rendered the deep waters more or 

 less uninhabitable. 



RECENT GEOGRAPHICAL DISCOVERY. 1 



After some introductory remarks referring to his 

 previous visit to Canada, Gen. Lefroy alluded to the 

 relations of geography to geology as instanced in the 

 changes in the earth's surface within historical times 

 by the operation of geological causes. A recent 

 German writer, Dr. Halm, has enumerated ninety- 

 six more or less extensive tracts known to be rising 

 or sinking. For example: Mr. R. A. Peacock has 

 accumulated evidence that the Island of Jersey had 

 no existence in Ptolemy's time, and Mr. A. Howarth 

 has collected similar proofs with regard to the arctic 

 regions ; and every fresh discovery, notably those of 

 the gallant and ill-fated DeLong and of Nordenskiold, 

 adds to the number. Professor Hull has reached 

 the conclusion that the land between Suez and the 



1 Address to the geographical section of the British associa- 

 tion at Montreal, Aug. 28, 1884, hy Glen. Sir J. H. Lefroy, 

 R.A., C.B., K.C.M.G., F.R.S., F.SA., vice-president of the 

 Royal geographical society, president of the section. 



