6 



MAXUAL OF THE MOI,LUSCA. 



tliG Brachiopoda, form the sub- class of Molluscoida. In the 

 first edition the Tunicata were described in detail, but they are 

 omitted in this for reasons stated in the iDieface. 



Eiye of these modifications of the moUuscan type of organi- 

 sation were known to Linnaeus, who referred the animals of all 

 his genera of shell-fish to one or other of them ; * but unfortu- 

 nately he did not himself adopt the truth which he was the 

 first to see ; and here, as in his botany, employed an artificial, 

 in preference to a natural method. 



The systematic arrangement of natural objects ought not, 

 howeyer, to-be guided by conyenience, nor " framed merely for 

 vlio purposes of easy remembrance and communication." The 



Fig. 7. A Bivalve. t Tig- »• ^ Tunicary. J 



true method must be suggested by the objects themselyes, by 

 their qualities and relations ;— it may not be easy to learn,— it 

 may require perpetual modification and adjustment, — but inas- 

 much as it represents the existing state of knowledge it will aid 



■» Tlie Linnaean tj-pes were— Sepia, Limax, Clio, Anomia, Ascidia. Terebratulci 

 vras included with Anomia, its organisation being unknown. 



t Mya truncnta, L. |. From Forbes and Hanley. 



I Ascidia menttda. Mull. Ideal representation ; from a specimen dredged by Mr 

 Bowerbank, off Tenby. 



