CLASSIFICATIONS IN NATURAL HISTORY. 20$ 



At the present time hardly two standard authors of text-books 

 of Zoology or Paleontology will be found to apply the no- 

 menclature of classification in the same way throughout ; that 

 is, they will not distribute the genera in the same manner, or 

 will give different value, or will apply different names to 

 orders, families, and classes. 



Selection of a Standard Classification. — It becomes necessary 

 to use some standard in the matter of classification, and Zit- 

 tel's *' Manual of Paleontology" may be selected as the stan- 

 dard in the present case. Editions of Zittel are published in 

 both German and French, but at the present time (1895) no 

 English edition has appeared.* 



Differences of Opinion regarding the Rank of the Characters 



The difference in usage of the nomenclature of classification 

 is determined by differences of opinion as to the taxonomic 

 value or rank of characters expressed by the organisms 

 rather than by any difference in recognizing the characters as 

 matters of fact. Classifications, therefore, although differing 

 in the hands of different authors, may be used with precision 

 when considered as descriptive of the combination of char- 

 acters expressed in actual organisms. 



There are several standard classifications of more or less 

 common use among paleontologists, three of which may be 

 here referred to: Claus and Sedgwick's, as given in "Ele- 

 mentary Text-book of Zoology," 1884; Zittel's classification in 

 " HandbuchderPalaeontologie," vol.1., 1 876-1 880; Nicholson 

 and Lydekker, " Manual of Paleontology," 3d Ed., 1889. 



Claus and Sedgwick's Definitions of the Nine Branches of the 

 Animal Kingdom. — Brief definitions of the nine branches, as 

 given by Claus and Sedgwick, are as follows, viz, : 



^'■Protozoa. — Of small size, with differentiations within the 

 sarcode, without cellular organs, with predominating asexual 

 reproduction. 



" Ccclcntcrata. — Radiate animals segmented in terms of 

 2, 4, or 6 ; mesoderm of connective tissue, often gelatinous; 



*A briefer text-book in German has appeared : " Grundziige der Palseon- 

 tologie (Palseozoologie)," von Karl A. von Zittel, pp. i-viii, 1-97 1. and 204S 

 figures; Munich, 1895. An English translation of this work, with some revision 

 by American paleontologists, is in preparation. 



