454 



SCIENCE 



[N. S. Vol. XXXVII. No. 951 



course expressed his preferences in deciding 

 disputed questions of nomenclature, of which 

 a few might well be referred to the Interna- 

 tional Zoological Congress for arbitration. 



As already stated, the number of species 

 and subspecies of North American land mam- 

 mals is in round numbers about 2,150, without 

 including a considerable number described 

 late in the year 1912. The first enumeration 

 comparable in geogTaphic area with Mr, Mil- 

 ler's was published by True' in 1885, number- 

 ing 365 species and subspecies. This number, 

 according to Miller and Eehn,' had increased 

 by the end of the year 1904 to 1,450. Elliot, 

 in 1905, in his " Check List of the Mammals 

 of the Continent of North America, the West 

 Indies and the Neighboring Seas," ' included 

 1,940 forms of land mammals, he listing a con- 

 siderable number that have since, through the 

 work of monographers, passed into synonymy. 

 Doubtless when other groups are subjected to 

 this ordeal many listed in the present check 

 list will also lapse, so that the number now 

 fairly entitled to recognition may be esti- 

 mated at about 2,000. Probably many valid 

 additions are yet to be made from parts of 

 Central America now very imperfectly known. 



The task of preparing the present list could 

 hardly have fallen to more competent hands, 

 and mammalogists owe a debt of gratitude to 

 its author for the great aid it will be to them 

 in their work. It is to be regretted, however, 

 that so unusual and confusing a system of 

 classification has been adopted, the scheme 

 being based on specialization, the sequence of 

 the higher groups being determined by the 

 amount of their departure in structure from 

 the most " primitive " or " generalized " mam- 

 malian type, and not on affinity or genetic re- 

 lationship. The arrangement therefore will be 



^True, F. W., "A Provisional List of the Mam- 

 mals of North and Central America and the West 

 Indian Islands," Proc. V. S. Nat. Mus., Vol. 7, 

 1884, pp. 587-611 (appendix, 1885). 



""Systematic Results of the Study of North 

 American Land Mammals to the Close of the Year 

 1900," Proc. Boston Sac. Nat. Hist., Vol. 30, pp. 

 1-352, December, 1901. 



Tield Columbian Museum, Zool. Ser., VI., 1905. 



very confusing and unprofitable to nine tenths 

 of the users of Mr. Miller's book, who have 

 been led to suppose that the purpose of a sys- 

 tem of classification designed for general use 

 was to indicate, so far as possible in a linear 

 sequence, the affinities of the animals classi- 

 fied. The classification here adopted may 

 serve the purpose for which it was intended — 

 an expression of the relative degree of spe- 

 cialization among the ordinal groups of mam- 

 mals; but it is rather startling to the uniniti- 

 ated to find the two ends of the series repre- 

 sented, respectively, by the Monotremes and the 

 Cetacea, and the Primates flanked on one side 

 by the Edentates and on the other by the 

 Artiodactyls : In other words, to find an other- 

 wise admirable check list of the mammals of a 

 continent arranged in conformity to a scheme 

 of classification which ignores genetic rela- 

 tionships and therefore is out of touch with 

 current faunistic and systematic work on re- 

 cent mammals. J. A. A. 



General Chemistry of the Enzymes. By 

 Hans Euler, Professor of Chemistry in the 

 University of Stockholm. Translated from 

 the German by Thomas H. Pope. New 

 York, John Wiley and Sons. Pp. 323. 

 The chemical changes which are taking 

 place continually in plants and animals fall, 

 for the most part, under that branch of sci- 

 ence which is called organic chemistry. It is 

 characteristic of organic reactions that they 

 proceed slowly, though their progress can 

 often be hastened by the addition of small 

 amounts of particular substances, the so- 

 called catalysts. This property of hastening 

 the speed of organic reactions by supplying 

 an appropriate catalyst is wonderfully de- 

 veloped in living organisms, because the ele- 

 ment of time is all-important to them. The 

 catalysts which occur in organisms are given 

 the general name of enzymes. In many cases 

 they can be readily separated from the cells of 

 the organism and they are accordingly con- 

 sidered to be organic chemicals, probably of 

 complex composition, but without organized 

 or cell structure. Up to the present time no 

 one has succeeded in crystallizing or vaporiz- 



