DETERMINATION OF GENERIC TYPES, ETC. 65 



advisable to give preference to the best figured form. Again, the best 

 known species may be preferred under some circumstances. On the 

 other hand, conditions may be present which would make it decidedly 

 preferable to select as type a species which is the most common, and 

 on this account preference is frequently shown to species bearing the 

 specific name communis (see p. 64). To show preference to a species 

 which is easily obtainable is undoubtedly a good policy to follow, for 

 no matter how well a given animal is described the advance in anatom- 

 ical knowledge may make it advisable that the species be restudied, 

 and in this event the more easily obtainable the species is the better 

 the opportunity for the necessary study. In some cases it may be 

 distinctly preferable to select as type species some form of which the 

 original type specimens are known to be in existence. In the case of 

 animals with separate sexes, it will usually be distinctly better to 

 select as type some species for which both sexes are known. 



19. THE ORIGINAL GENERIC NAME TO GO WITH THE GREATER NUMBER OF SPECIES. 



RECOMMENDATION. In dividing a genus containing a large number of 

 species, it is well to select the type from the group which contains the largest 

 number of species. 



This recommendation is intended to preserve the old generic name, 

 so far as possible, for as many original species as possible. It was 

 proposed by De Condolle. 



20. SPECIAL POINTS TO BE CONSIDERED IN CONNECTION WITH GENERA OP PARASITIC 



GROUPS. 



RECOMMENDATION. In parasitic genera select, if possible, some species 

 which occurs in a food animal or in man, or in some very common and wide- 

 spread host. 



The justice of this recommendation will probably appeal to all per- 

 sons who seriously consider the various possibilities involved. 



In the first place, if a given species is type of a genus, its name is 

 less likely to be subjected to change than are the names of species 

 which are not types. It would be well, therefore, to take advantage 

 of this greater chance of stability in order to protect from changes the 

 names of animals which are used by others besides zoologists. Thus, 

 the parasites of man and of the domesticated animals come into consid- 

 eration in the medical and legal writings of authors in human and 

 comparative medicine and in meat inspection, and a change of name of 

 animals or plants which come into consideration in such literature is 

 of infinitely greater inconvenience and difficulty than is the case with 

 a name occasionally used by only a few systematic helminthologists. 



Again, if type species are selected from hosts which are common 

 and of wide distribution, they can be more easily obtained for future 

 study. 



6328 No. 7905 5 



