PRINCIPLES, CANONS, AND RECOMMENDATIONS. 41 



1. Of names the equal pertinency of which may be in question, 

 preference shall be given to that which is open to least doubt. 



2. Of names of undoubtedly equal pertinency, (a) that 

 founded upon the male is to be preferred to that founded upon 

 the female, (b) that founded upon the adult to that on the young, 

 and (c) that founded on the nuptial condition to that of the pre- 

 or post-nuptial conditions. 



3. Of names of undoubtedly equal pertinency, and founded 

 upon the same condition of sex, age, or season, that is to be pre- 

 ferred which stands first in the book. 



CANON XVIII. Preference between competitive generic 

 names published simultaneously in the same work, or in two 

 works of the same actual or ostensible date (no exact date being 

 ascertainable), is to be decided as follows : 



1. A name accompanied by the specification of a type takes 

 precedence over a name unaccompanied by such specification. 



2. If all, or none, of the genera have types indicated, that 

 generic name takes precedence the diagnosis of which is most 

 pertinent. 



6. Of the Retention of Names. 



CANON XIX. A generic name, when once established, is 

 never to be cancelled in any subsequent subdivision of the 

 group, but retained in a restricted sense for one of the con- 

 stituent portions. 



REMARKS. This rule, adopted from the B. A. Code, has been generally 

 accepted as sound in principle, but as difficult of application, especially in 

 relation to what portion of the original genus, when subdivided, shall retain 

 the original name; in other words, what, in accordance with modern 

 usage, shall be taken as the ' type ' of the original genus, in cases where no 

 type is specified. 



In recommending this provision the B. A. Committee urged: "As the 

 number of known species which form the groundwork of zoological science 

 is always increasing, and our knowledge of their structure becomes more 

 complete, fresh generalizations continually occur to the naturalist, and the 

 number of genera and other groups requiring appellations is ever becoming 

 more extensive. It thus becomes necessary to subdivide the contents of old 



