'/.oology and Botany. 407 



strong as to act sensibly on the surface of the crust ; in that case 

 he had found that the spines would fall off. 



Thursday, \2>th August — Many of the members being en- 

 gaged to dine at Salthill, Kingstown, made a botanical and en- 

 tomological excursion in the forenoon to Killiny Hill ; and the 

 meeting of the Section was, therefore, merely formal. 



Friday, \4:th Augtisf. — The Section having met this morn- 

 ing, according to appointment, at the Botanical Garden of the 

 Dublin Society at Glasnevin, the meeting was adjourned to the 

 following day, and Mr Mackay conducted a party on a botani- 

 cal excursion to Portmarnock and Hill of Howth. 



Satui'day, \5th August. — Professor Agassiz delivered an 

 extempore discourse on the principles of classification in the 

 animal kingdom in general, and among the mammalia in par- 

 ticular. Although the general groups of animals are im- 

 pressed with such characters as to be easily recognised, and 

 to admit of little doubt, yet their order and succession has 

 been determined by no general principle. This appears from 

 the discrepancy in the positions assigned to them by the most 

 eminent systematlsts, each of whom has assumed arbitrarily 

 some one organ, or system of organs, for the basis of his ar- 

 rangement. Professor Agassiz, after adverting to some Ger- 

 man naturalists who alone have sought after a general prin- 

 ciple, and aspired to the character of " philosophic naturalists,"" 

 passed in review the classes of the animal kingdom, each of 

 which he shewed to exhibit, in an eminent degree, the de- 

 velopement of some one of the animal functions. While verte- 

 brate animals (with man their type) arrive at the greatest per- 

 fection in the organs of the senses ; the invertebrate offer, in 

 the class of worms, the representative of the system of nutrition ; 

 in Crustacea, of circulation; in Insects, of resplratlcji ; and in 

 mollusca, of generation. Tiie Professor next proceeded to de- 

 monstrate In what manner the subclasses of vertebrate animals 

 derive each its peculiar character from some one clement of the 

 aninsal economy. This j>redominant element is the bony skele- 

 ton in fishes, the muscular structure in reptiles, the sensibility of 

 tlic nervous system in birds, and the perfection of the senses in 

 mammalia, which therefore reproduce the distinguishing cha- 

 racter, and constitute the tyjie of vertebrate animals. He next 



