Mr. Lyell's Address. 4H 



mechanical contrivances and combinations of form and structure 

 which the fossil representatives of that class exhibit. 



The account also of the Cephalopodous Mollusca, so many thou- 

 sands of which are scattered through the strata, and which until 

 very recently have presented so obscure a problem to the naturalist, 

 is full of original observation. The history of the animals which 

 formed the Belemnites, of which it appears that nearly one hun- 

 dred species are now known, and the proofs adduced that they 

 were provided with ink-bags like the cuttle-fish, the description 

 also of the fossil pen-and-ink fish, or Loligo, and other sections of 

 this part of the Treatise, carry our information respecting the fnmily 

 of naked Cephalopods much further than was ever attempted in any 

 previous work. Nor should I omit to mention the exposition of an 

 ingenious theory for the use of the siphuncle and air-chambers of 

 the Ammonite, which, whether confirmed by future examination or 

 not, becomes in the author's hands the means of conveying to the 

 reader a clear and well-defined notion of the varied forms and 

 complicated structure of these shells, and of awakening a lively de- 

 sire to understand their singular organization. 



I may also recall to your notice the just and striking manner in 

 which certain physical inferences are drawn from the conformation 

 of the eyes of extinct Crustacea, such as the Trilobite. The most 

 delicate parts of these organs are sometimes found petrified in 

 rocks of high antiquity, and it is justly observed, that such opti- 

 cal instruments give information regarding the condition of the 

 ancient sea and ancient atmosphere, and the relations of both these 

 media to light. The fluid in which these marine animals lived at 

 remote periods must have been pure and transparent to allow the 

 passage of light to organs of vision resembling those of living Cru- 

 staceans ; and this train of reasoning naturally leads us still further, 

 and to more important consequences, when we reflect on the general 

 adoption of the undulatory theory of light, and the connexion be- 

 tween light, heat, electricity, and magnetism. 



I have heard it objected, that the zoologist and botanist had 

 already advanced such abundant proofs of design in the construc- 

 tion of living animals, and plants, that the auxiliary evidence of 

 palaeontology was useless, and that to appeal to fossils in support of 

 the same views was to add weaker to stronger arguments. In 

 the living animal, it is said, we can study its entire organization, 

 observe its habits, see the manner in which it applies each organ, 

 and so verify with certainty the ends for which any particular mem- 

 ber was formed and fashioned. But in the case of the fossil, we 

 have first to infer the greater part of the organization from such 

 parts as alone remain, and then further to infer from analogy the 

 habits and functions discharged, and lastly the former conditions of 

 existence of the creatures so restored. If then we occasionally fail 

 into error when speculating on the use of the organs of living spe- 

 cies, how much more easily may we be deceived in regard to the 

 fossil ! 



In answering this objection, it cannot be denied that the data 

 ;3 G 2 



