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THE AMERICAN NATURALIST [Vol. XLVIII 



very few animals have been thoroughly explored, yet in the dis- 

 tant future, in the millennium, it can not be doubted that every 

 genus, even every species will have been examined in toto in every 

 stage of its development and life-history as thoroughly as our 

 instruments and eyesight will allow, and perhaps a whole vol- 

 ume or several volumes will be devoted to every animal form. 

 At present, however, it is a waste of ink to consider a future so 

 far away. A more pressing duty is to consider how far modern 

 methods of superficial diagnosis fulfil the obligations placed 

 upon systematists not to give an exhaustive analysis of animal 

 forms, but to give suffieietit data to meet the searching demands 

 of phylogenetic classification. 



We are aware of the fact that the convinced and determined 

 systematist does not maintain that the method of superficial 

 diagnosis does meet or is intended to meet the demands we have 

 been indicating. If he reads as far as this and does not throw 

 aside this paper in contempt, he is ready with eager forefinger 

 and glib apology to convict us of begging the question that sys- 

 tematic zoology can be ever anything, or should be ever any- 

 thing more than we have said. 



It is often argued that the superficial diagnosis of the syste- 

 matic worker is simply a provisional diagnosis awaiting the con- 

 firmation of the anatomist. A plausible defence of the provi- 

 sional diagnosis is advanced by many workers in perfect good 

 faith winch it is now necessary to anticipate and examine. 



This argument defends the provisional diagnosis on two 

 grounds: (1) The advertisement theory; (2) the recognition 

 mark theory. 



The supporters of these theories admit that the provisional 

 diagnosis in no way settles either an animal's systematic posi- 

 tion or its validity as a species. But it is alleged to be of value 

 and should be encouraged because it advertises the existence of 

 a presumptive new form which would otherwise remain un- 

 known and overlooked in the store rooms of the museum and 

 laboratory, and because in giving an account of the external 

 parts, at all events, the systematist is describing those features 



