Hyatt.] 364 [June 7, 



In the other school, a zoologist or paleontologist makes greater 

 allowance for the variability of organic bodies, becomes distrustful of 

 all single characteristics, or combination of single characteristics, and 

 endeavors to combine all possible sources of information in his defi- 

 nition of groups. 



The former naturally tends to the formation of large generic 

 groups, those which can be approximately distinguished by some 

 salient structural characteristic, and the latter to the division of 

 these large groups into many minor ones, in order to show the nat- 

 ural affinities and derivation of animal forms. 



The former leads to the artificial method of classification which has 

 always, without the slightest reason, been claimed to be the more 

 useful, and the latter to the approximately natural method. The differ- 

 ences are most prominently presented in one, and in the other these 

 are considered of no more importance than any other class of charac- 

 teristics. The first is certainly the most imperfect and conventional; 

 and why its defects, which are openly confessed, should be regarded 

 as recommendations for its adoption, or how it becomes by means 

 of its confused imperfection more convenient, is equally incompre- 

 hensible. Is it more convenient to consider under the same head 

 the genus Antipathes, one of the Alcyonoid corals and the Aplysinse 

 among the Keratose Sponges, because their skeleton is identical 

 structually? This would be considered absurd; but undoubtedly, if 

 found fossil no purely Paleontological student could show an essential 

 difference between them, and according to the demands of conven- 

 ience, as understood by most of them, this absurdity ought to be 

 committed. Innumerable instances might be quoted of a similar 

 description, but it is unnecessary; practically the natural system of 

 classification is always adopted after a certain lapse of time, and the 

 different artificial and single character systems become obsolete. 



I do not mean to underrate the great service done to the Natural 

 History of the Ammonoid and Nautiloid Groups by Dr. Waagen. 

 Waagen's treatise on the Annular Muscle of the Nautilus and Am- 

 monites, the characteristic position and probable homology of the 

 Aptychus with the similarly situated coverings of the heart in 

 Nautilus Pompilius and observations on the length of the living 

 chamber, are solid and permanent contributions, which cannot be 

 too highly appreciated; but the mode of application of these to the 

 classification of the Ammonoids is, according to my views, entirely 



