OF CONCHOLOGY. 89 



day, whether the opinions of the observer incline to accept or to 

 reject it. 



Again, the whole system of nomenclature is only useful as an 

 index to the members of the animal kingdom. The more accu- 

 rate, full, and discriminating the index, the greater its value in 

 generalization, and the more accessible becomes a true apprecia- 

 tion of natural laws. On the other hand, the combining in 

 unnatural and heterogeneous groups, for purposes of conveni- 

 ence, forms which exhibit structural differences of greater value 

 than the characters of the united group, is a course directly in 

 opposition to all principles of science, and one which lays the 

 greatest obstacles in the path of study. The argument used 

 against an extended nomenclature, of its overtaxing the memory, 

 &c., as Dr. Morch truly observes, is unworthy a moment's con- 

 sideration from scientific minds, and is only adapted for the non- 

 scientific and popular masses. Such a train of reasoning carried 

 to its logical conclusion would take us back to the system of 

 Linnaeus, or Aristotle himself. 



In these remarks I must not be understood as reflecting in any 

 way upon the very valuable labors of the authors above men- 

 tioned. To Mr. Davidson we are under great obligations, for 

 restraining the premature cacoethes nommandi in the group of 

 BraeJiiojyoda. However, I believe the time has arrived when 

 our knowledge of the internal structure of these mollusks is 

 sufficient to warrant their separation into natural groups, which 

 should no longer be left without definite appellations. 



The position of the Brachiojjoda with respect to the other 

 classes of the animal kingdom has been frequently the subject of 

 discussion, but of late years naturalists have almost unanimously 

 agreed in considering them as closely allied to the Ascidians 

 and Polyzoa, and as occupying a place in that subdivision of the 

 subkingdom Mollusca of Cuvier, to which the name 3IoUuscoidea 

 has been applied. The researches of Mr. E. S. Morse into the 

 embryology of Terehratulina septentrionalis, would seem to sub- 

 stantiate this view entirely, and the only question still undecided 

 would seem to be whether the Bracliiopoda or the Ascidia should 

 be considered as the most nearly allied to the LamellibrancJiiata. 

 As naturalists have generally come to the conclusion that linear 

 classification is impossible, this point, though of interest, can 

 hardly be said to be of great importance. But, more recently, 

 Mr. Morse,* after enjoying great facilities for the study of the 

 living animal of Lingula, has announced as his opinion, that the 

 Brachiopods and Polyzoa must be removed from the mollusca 



* Sillimau's Journal, July, 1870, p. 100. 



