ANNIVEBSARY ADDRESS OF THE PEESIDENX. IxXV 



life, concurrent with, the passage of time, is evident, especially to 

 geologists ; but of the way in which these changes have been carried 

 out, I own to not yet seeing a sufficient explanation. Have ter- 

 raqueous changes led to variations in the structure of animal life 

 by the law of Natural Selection among the few that best adapted 

 themselves to the changed conditions ? or was it by a gradual modifi- 

 cation induced in the many, in consequence of the general change 

 to which they were all subjected ? or was there some law in time, or 

 of a character yet unknown to us, cooperating with the change in 

 conditions, to produce those singular and extraordinary changes and 

 variations of structure of which we have now such full evidence 

 as to fact, but so little as to theory ? 



These are some of the problems towards the solution of which I 

 look with great hope in the continuance of these most interesting 

 deep-sea researches, important alike to the naturalist, the physicist, 

 and the geologist. 



P.S. The few particulars in this Address relating to deep-sea tem- 

 peratures were collected some twenty years since for a paper never 

 published. As they form fitting antecedents to the more important 

 recent researches, I have incorporated part of them here, leaving 

 possibly some of the intermediate work rather incomplete. 



Note. — Since the greater part of this Address was printed, Mr. 

 Jefireys informs me that he has now, through the kindness of Prof. 

 Loven, examined the shells procured in the Swedish expedition of 

 1869 by dredging on the Josephine Bank and off the Azores, at 

 depths ranging from 110 to 790 fathoms ; and that nearly all these 

 shells belong to the same species as those procured in the ' Porcupine ' 

 expeditions at similar depths. 



