230 THE ZOOLOGIST. 



Classification of Birds : an Attempt to diagnose the Subclasses, 

 Orders, Suborders, and some of the Families of existing Birds. 

 By Henry Seebohm. 8vo, pp. 53. London : R. H. Porter. 

 1890. 



This is an attempt to classify existing Birds in groups which 

 are capable of being diagnosed, and represents an enormous 

 amount of labour. In little more than fifty pages Mr. Seebohm 

 has set down the well-considered results of his examination of 

 the Osteology, Myology, and Pterylography of as many forms as 

 it was possible to examine, bearing in mind that many species 

 are known only from skins forwarded by collectors, and their 

 affinities consequently can be only surmised from external 

 characters. 



We infer, however, from his diagnoses, that he has been able 

 to see either freshly killed or spirit specimens representative of 

 every one of the suborders named by him, and probably represen- 

 tatives of most of the families belonging to these suborders which 

 are thirty-six in number. 



In selecting characters he has been careful, as he states in 

 his Introduction, to choose those which are supposed to denote 

 affinity, — in other words to be due to inheritance from common 

 ancestors ; and so far as possible to avoid such as only denote 

 analogy, that is to say such as are only instances where like 

 causes have produced like effects. 



It is, however, very difficult to tell which characters have been 

 inherited and which have been independently acquired. In many 

 cases it is only possible to guess, in others it is absolutely 

 impossible to form any opinion at all. It may, perhaps, be fairly 

 assumed that the more complicated a character is, the less 

 chance is there that it can have been independently acquired by 

 two groups. It may also be taken for granted that it is very 

 much more difficult even for a simple character to be independ- 

 ently acquired than to be independently lost. 



To ascertain then whether a given character denotes affinity, 

 or even analogy, is the first difficulty of classification ; the second 

 being to ascertain the relative value of the different characters. 



On this point, unfortunately, no rule can be laid down, though, 

 as Mr. Seebohm remarks, there are certain laws which govern 



