160 



INTRODUCTION TO ZOOLOGY. 



conchology on philosophical principles, for it fixed the attention 

 of men more upon the covering than upon the humble animal 

 contained within. Such was not the spirit with which 

 Aristotle regarded them ; for the structure and habits of the 

 creatures were the main objects of his study, while their 

 relations to the other animated beings by which they were 

 surrounded, and their own mutual affinities, were not for- 

 gotten.* To conchology as a science, Pliny added nothing 

 that Aristotle did not supply; but he has furnished some 

 anecdotes regarding its economical applications, and has graced 

 its history with some amusing fictions. 



Fig. 153. CYPU^SA. 



Passing from the ancients to the distinguished Swede, 

 whose labours in the last century have done so much for the 

 advancement of natural science, we come to the system of 

 Linnaeus, which was perfected in 1766. Shells were at that 

 time arranged into three primary divisions univalve, bivalve, 

 and multivalve according to the number of pieces of which 

 the shell was composed. The animals were spoken of as 

 naked mollusca, when, like our common slug, they were 

 destitute of an external shelly covering, and as testaceous 

 mollusca (testa, a shell), when, like the garden snail, they were 

 furnished with this protection. In the system of LinnaBus, 

 the testaceous mollusca occupy one order by themselves, in 

 which there are four sections multivalve, bivalve, univalves 

 with a regular spire, and univalves without a regular spire. The 

 naked tribes are placed in the order denominated "mollusca," 

 along with worms, zoophytes, and star-fishes. 



" In estimating," says Dr. Johnston, "the merits of this 

 system, it is not fair to look back from our present vantage- 

 ground, and magnify its defects by a comparison with modern 



* The few remarks here made on the progress of conchology are taken 

 from an article by Dr. Johnston, in Magazine of Zoology and Botany, 

 vol. ii. page 238. 



