1868.] 



on Deep-sea Dreclgings. 



i 



195 



rapid and considerable, it might cause the extinction over those areas of a 

 large proportion of the species which inhabited them ; whilst others would 

 migrate in the direction of the temperature most congenial to them, and 

 transfer to new localities those types which could no longer exist in their 

 previous habitats, — thus establishing the Colonies of M. Barrande. If, on 

 the other hand, such a change of Temperature were more gradual, the 

 greater part of the species constituting the Faunse of the areas over which 

 it occurred might adapt themselves to it, undergoing such modifications 

 in their structure and habits as might be considered sufficient to differen- 

 tiate them specifically, whilst retaining so many characters of general simi- 

 larity as to constitute "representative species" *. 



X. The ingenious suggestion of Dr.Wallichf that the nature of the Animal 

 life found on the sea-bottom may not unfrequently afford some clue to the 

 history of its changes of level, — his discovery at great depths of a type 

 (the Ophioeoma granulata) which is essentially littoral being indica- 

 tive of slow progressive subsidence, — may be extended with some proba- 

 bility to changes of submarine climate ; for where any species is found 

 abundantly as a littoral form, its presence at great depths in the same 

 region would seem to indicate that the subsidence of the bottom has not 

 been attended with any considerable alteration of temperature, whilst its 

 absence on neighbouring parts of the same area may be fairly taken as 

 evidence of such a change. 



The preparation of a detailed list of the Species found in each locality, 

 with the depths from which they were brought up, furnishing the justifi- 

 cation of the general statements made in this Report, has been kindly 

 undertaken by Professor Wyville Thomson, who will present it at the 

 earliest practicable date ; and he will also describe the new and very 

 remarkable forms of Vitreous Sponges we have obtained, this being a group 

 to which he has already given special attention. — I shall myself lose no time 

 in preparing an account of the Rhisopocls we have collected, availing 

 myself of the kind assistance of Professor Huxley, who has undertaken to 

 examine and describe the Organic components of our various specimens of 

 Chalk-mud, and of Professor Frankland, who will determine their Chemical 

 composition. 



We cannot but hope that when our Report shall have been thus completed, 

 it may be found not unworthy of the Royal Society by which our inquiry 

 was promoted in the first instance, and of the Government which provided 

 the means for its prosecution, and that the results we have obtained may 

 be regarded as sufficiently important to justify its extension both in range 



* It will be obvious to every one who is conversant with Sir Charles Lyell's ' Prin- 

 ciples,' that in the views above stated I have simply extended the doctrines long since 

 promulgated by that great Master of the Philosophy of Greology. 



t The North-Atlantic Sea-Bed, pp. 149-155. 



