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aniiuals wliich are entirely iiKlependent of one another. The conclusions based 

 upon the facts of anatomical and morjiUological research mnst always give way to 

 the direct proofs of biology. The significance of cori>oreal characters is establislied 

 by biology. Anatomy and morphology give the quantity, biology determines 

 the quality. It is therefore obvious that the classifier should not let himself 

 be guided in his judgment solely by a consideration of the quantity of bodily 

 characters, but always keep in mind the higher criticism of (piality. If he does 

 this, he will not easily fall into the error of treating two groups of individuals 

 as being of the same classificatory category (variety, species, genus, etc.), it 

 'biological considerations are against it. If the classifier had no other guide 

 than corporeal similarities and differences, the classification would merely be an 

 artificial arrangement, without regard to the true connection between the animals 

 classified. Such a classification, perhaps very useful for the mere collector, 

 might be likened to an arrangement of minerals according to their external 

 features, without any regard to their chemical composition. 



Although there are no biological data available of most animals, of which 

 we know nothing but what the dead bodies or portions of them (embryo to 

 adult) tell us, the scientific classifier has nevertheless another guide. This 

 guide is the principle of judging from analogy (the word used in the logical 

 sense). We give two illustrations. If in a certain country the spring- and 

 stiramer-broods of a certain group of species have been proved to be diS"erent 

 in all the s])ecies examined, we may safely conclude that tliey difter also in 

 those species of the grouji which have not yet been examined. Therefore, forms 

 of that group of which it is only known that they difter in the same way 

 as the horodimorphic forms of the better-known species must also be treated as 

 seasonal varieties, and not as distinct species. As we have found that the 

 genital armature, thougb individually variable, does not exhibit any seasonal 

 differences in those species of Lepidoptera of which forms proved to be seasonal 

 have been examined by us, we are bound to conclude that Leijidoptera which 

 do constantly show differences in those structures are not seasonal forms of one 

 species. The premiss is the better established, and hence the conclusion is the 

 more likely to be correct, the more species have been examined. This deductive 

 reasoning, though logically exact, will never give us ceitainty. For the animals 

 as we know them are the product of evolution ; the result of evolution is 

 dependent on the nature of the animal and of the evolving extraneous factors ; 

 these extraneous factors being independent of the animal, their combination 

 with the internal factors — which combination dete-mines the line of develop- 

 ment—depends on accident ; results determined by accident cannot be deduced 

 from an a priori law. That means, we do not a priori know that what holds 

 good in all the cases examined is true also in every case not yet examined. 

 Nearly all the so-called "laws" in biology are nothing Imt more or less well- 

 formulated rules of jirobability admitting of excei)tioiis. A rule may apply to 

 every individual case within a certain group of animals ; but the further away 

 we g(j from that group, tlie greater becomes the chance of exci^ptions turning 



