138 SCIENCE SKETCHES. 



this applies to different names given in the same 

 work to the same group. 



It is certain that Clause 2 in this canon is based 

 on special peculiarities of ornithology, while Clauses 

 I and 3 are doubtless due to compromise among 

 ornithologists. The question of equal pertinency 

 of description is very often a subjective one, and 

 this rule gives room to individual judgment or 

 caprice, and this it is the business of the ** Code " 

 to eliminate. As to Clause 2 we may notice that 

 in most groups of animals, as in the fishes for 

 example, we cannot discriminate in any such way 

 between males, females, and young, or between 

 the various nuptial and non-nuptial conditions. 

 The clause is for ornithologists alone, and by 

 other naturalists it must of necessity be disre- 

 garded. Of synonymous names which admit of 

 positive identification, and which are printed in 

 the same book, we shall doubtless continue to use 

 that name which stands first upon the page, without 

 regard to other considerations. I believe that the 

 law of primogeniture is made to apply in the case 

 of twins. The chief aim of the law of priority, like 

 that of the law of primogeniture, is not the survival 

 of the fittest, nor yet justice, but simply fixity. 

 The present Canon XVII. will not secure fixity. 

 The same remarks apply to Canon XVIII., which 

 refers to synonymous genera of the same date of 

 publication. 



In the cases of Canons XXI. and XXIII. , which 

 treat of the restriction of composite genera in which 

 no type has been clearly indicated by the author, 

 some important matters are left obscure. It is 



