Life in the Deep Sea. 291 



for zoological science, determined in this case to address him- 

 self exclusively to that very limited class whose pecuniary and 

 cerebral developments go hand in hand. The less wealthy 

 student to whom costly pamphlets are unattainable luxuries need 

 not, however, lament his fate, as a concluding extract from 

 Dr. Wallich will give him the cream of the whole matter, and 

 show, for his economical edification, that : 



1. "The conditions prevailing at great depths, although 

 differing materially from those which prevail near the surface of 

 the ocean, are not incompatible with the maintenance of life. 



2. " Assuming the doctrine of single specific centres to be 

 correct, the occurrence of the same species in shallow water 

 and at great depths, proves that it must have undergone the 

 transition from one set of conditions to the other with impunity. 



3. "There is nothing in the nature of the conditions pre- 

 vailing at great depths to render it impossible that creatures 

 originally, or through acclimatization, adapted to live under 

 them should become capable of living in shallow water, provided 

 the transitions be sufficiently gradual, and hence it is possible 

 that species now inhabiting shallow water may at more anterior 

 periods have been inhabitants of great depths. 



4. " On the one hand, the conditions prevailing near the 

 surface of the ocean render it possible for organisms to subside 

 after death to the greatest depths, provided every portion of 

 their structure is freely pervious to fluid ; on the other hand, 

 the conditions prevailing at great depths render it impossible 

 for organisms still constituted to live under them to rise to the 

 surface, or for the remains of these organisms after death to make 

 their appearance in shallow water. 



5. "The discovery of even a single species living normally 

 at great depths warrants the inference that the deep sea has 

 its own special fauna, and that it has always had it in ages past ; 

 and hence that, many fossiliferous strata, heretofore regarded 

 as having been deposited in comparatively shallow water, have 

 been deposited at great depths." 



