Mabch 5, 1909] 



SCIENCE 



389 



tempts to classify the bacteria. It will give 

 us a sound foundation upon which to build 

 our systematic groups. It will give us a 

 simple and natural nomenclature in place of 

 the unwieldy generic names in use at present, 

 and wiU do away with the tendency so no- 

 ticeable now to use trinomial or even quad- 

 rinomial names. 



Besides pointing out the proper way to 

 work out the classification of the bacteria the 

 authors have set us an example of just how 

 to go about the work by their careful study 

 of the Coceacese. They collected 500 different 

 strains of cocci from different sources and 

 submitted each one to a series of eleven defi- 

 nite, and in most cases, quantitative tests. 

 The frequency curve for each character was 

 plotted, the modes determined, and these 

 modes were taken as the bases for the estab- 

 lishment of the various groups. The eleven 

 characters were chosen after due deliberation 

 and while there may be a difference of opinion 

 as to the relative value of these characters 

 and others which might have been selected, 

 yet we must agree with the authors when they 

 say that the eleven tests chosen furnished 

 sufficient information to warrant the recog- 

 nition of the most important natural groups. 

 A further study of the correlation of these 

 characters seems to point to the fact that 

 these systematic units are marked by the gen- 

 eral association of a number of independent 

 characteristics. Such an association can be 

 explained, our authors say, only on the ground 

 of relationship, therefore the classification 

 which they have arrived at is a natural one, 

 and one which meets the requirements of ex- 

 pressing the natural relationships of the dif- 

 ferent groups. 



The authors find eight genera among the 

 Coecacea3, each of which they define and dis- 

 cuss. To the bacteriologist familiar with the 

 earlier classifications some very striking and 

 totally unexpected results appear. First of 

 these is the importance of pigment production 

 as brought out by this method. Hitherto it 

 has been taken for granted that such an easily 

 modifiable character as the production of pig- 

 ment was scarcely even of varietal rank. 

 But a study of chromogenesis by the biomet- 



rical method shows that the production of the 

 various pigments' is the property of certain 

 well-defined types, and when we take into 

 consideration the singularly perfect correla- 

 tion between this property and the fermenta- 

 tion of the sugars, and with other characters, 

 we must agree with the authors that it is 

 really of genetic significance. Second, we 

 find that the authors lay little stress on such 

 characters as the shape and markings of col- 

 onies on gelatin or agar, the shape of the 

 liquefaction in the gelatin stab, the luster or 

 surface appearance of agar streaks, characters 

 which we have been in the habit of consider- 

 ing important. They show that for the most 

 part these characters are but the result of 

 differences in general vigor of growth and in 

 the rate of liquefaction of the gelatin. They 

 summon sufficient evidence to support their 

 position so that we are forced to agree with 

 them. But they are careful to state that 

 their conclusions apply only to the Coecaceae 

 and that some of these characters may be 

 found important when other groups are 

 studied. 



The book closes with a summary of the 

 genera and species of the CoceaccEe, an admir- 

 able key to these genera and species, and 

 finally a complete bibliography and author 

 and subject indexes. 



While the work on the Coceacese is most 

 admirably done and gives us a working basis 

 for all future study of these forms, yet its 

 real worth is not in its own intrinsic value, 

 but in its immense suggestiveness for all fu- 

 ture work in the classification of other groups 

 of bacteria. We hope that this will be but 

 the first of a long series of monographs deal- 

 ing with other groups of the bacteria, all 

 worked out along the lines which these authors 

 have so well marked out for us. 



f. p. gorham 



Brown Univeksitt 



A Treatise on Gold and Silver. By Walter 

 E. Crane, Ph.D. New York, John Wiley & 

 Sons. 1908. 



The preface states that " The object of this 

 work with others of a series is to give a com- 

 plete and accurate record of the development 



