968 



SCIENyUE. 



[N. S. Vol. XIV. No. 364. 



Inevitably, also, the work is very uneven. 

 Professor Chester has been obliged to use as his 

 data the descriptions published by the numerous 

 bacteriologists, and inasmuch as these descrip- 

 tions vary so widely in their accuracy and in 

 the extent of the details given, there is con- 

 siderable difference in the completeness of the 

 descriptions of species listed. But this, of 

 course, cannot be laid to the fault of the author, 

 but rather to the incompleteness and irregu- 

 larity of the original descriptions. 



Two phases of this work are of especial value, 

 and bacteriologists will owe a debt to Professor 

 Chester for introducing them. The first is the 

 substitution of a new, descriptive word for the 

 long, frequently verbose descriptions which 

 have been widely used by bacteriologists. The 

 single word ' arborescent ' is quite as descrip- 

 tive as the long phrase commonly found in 

 bacteriological descriptions. A careful study 

 of the essential characters of colonies, gelatin 

 growths, etc., has enabled Professor Chester to 

 select a comparatively small number of words 

 which are distinctively characteristic, and which 

 can almost always be used in place of the long 

 paraphrases. This makes it possible to reduce 

 the length of descriptions and to give them in 

 the form of terse sentences, with a few charac- 

 teristic adjectives. The work of describing 

 species is thus immensely simplified. The 

 second important addition is the arrangement 

 of analytical keys. This, in itself, is one of the 

 most important phases of the work. By the 

 use of these analytical keys it is quite easy to 

 trace any unknown species of bacterium very 

 quickly to its proper place in Professor Chester's 

 list, and then, by further study of a few care- 

 fully drawn descriptions, to determine whether 

 the unknown species corresponds with any of 

 those previously described. It is hardly neces- 

 sary to emphasize the immense value it will be 

 to bacteriologists to have all the known species 

 of bacteria systematically arranged and trace- 

 able by means of a skilfully devised key. In 

 these two respects the work of Professor 

 Chester will be of the utmost assistance to 

 bacteriologists. 



The author adopts Migula's classification, 

 based upon fiagella, and this inevitably makes 

 a part of the arrangement of species uncertain. 



A large majority of the descriptions of bacteria 

 in literature contain no reference to fiagella. 

 In many cases, therefore. Professor Chester has 

 been forced to infer the presence or absence of 

 fiagella, and to classify the organisms to a 

 certain extent in this way by guesswork. 

 Without attempting to criticise the value of a 

 classification based upon fiagella, one cannot 

 but deplore the fact that the classification must 

 be based upon characters so difficult to deter- 

 mine. Most bacteriologists are more interested 

 in the physiological aspects of bacterial action 

 than in their structure, and it will be a long 

 time before the students of bacteria will be- 

 come so familiar with microscopic methods as 

 to be able to describe the distribution of fiagella. 

 For species described in past years, and for 

 those described by many bacteriologists for 

 years to come, we must expect that the dis- 

 tribution of fiagella will be a subject not at- 

 tended to with sufficient accuracy to make 

 possible a grouping of the species according to 

 Migula's classification. At all events, in this 

 determinative list of Chester's many of the 

 species are classified without any knowledge 

 of their fiagella, and their arrangement into 

 groups, as Professor Chester has arranged them, 

 is, in many cases, therefore, a pure matter of 

 inference. 



One other point may raise more criticism. 

 The author has taken the liberty to give names 

 to unnamed species. Where an author refers 

 to a bacterium by number, Chester has given 

 it a name. The original author will, therefore, 

 frequently quite fail to recognize an old friend 

 under a new name. The use of synonyms and 

 a good index of names, however, relieve some 

 of the difficulties arising from this wholesale 

 use of new names. 



It is, of course, inevitable that in a work of 

 this sort there will be some omissions. Each 

 bacteriologist who is particularly well ac- 

 quainted with a certain group of bacteria will, 

 naturally, be able to look through the treat- 

 ment of Professor Chester and find many points 

 to criticise. Each specialist will, doubtless, find 

 some omission and be inclined to differ with 

 the author in regard to the proper relationship 

 of the species. This, however, is inevitable 

 and does not at all detract from the usefulness 



