of the European Ornis, audits Causes. 299 



and that of the subspecies one hundred and forty times, as great 

 as with those ornithologists who form their opinions in accord- 

 ance with strict zoological notions. 



Reichenbach and Brehm assert that the notion of the species 

 is subjective : whoever requires a more convincing proof, over- 

 leaps the bounds of discretion. 



Strictly speaking, the only objectively distinct forms presented 

 by nature are the individuals. All further conceptions are sub- 

 jective views — separations on account of differences observed or 

 supposed to be observed. These differences belong objectively 

 to animals ; their estimation and relative valuation is exclusively 

 a subjective affair. It is a matter of subjective choice whether 

 we separate the Ostrich -like birds from the other birds as a 

 distinct class, or unite them with them ; it is a matter of sub- 

 jective choice whether we separate the Herons as an order from 

 the other Grall^e, and the Ducks from the other Natatores, or 

 place them together; it is a matter of subjective choice whether 

 we leave the Linnean genera Falco and Strix in their original 

 condition, or break them up into many genera, and so forth. 

 Lastly, it is a matter of subjective choice whether we separate 

 individuals as species, which only differ from each other by a 

 different state of plumage or a diffei'ent coloration, — e. g. Hali- 

 aetus leucorypkus, Pall, [unicolor, Gray), and H. macei, Temm., 

 or Larus heinei, Hom., and L. canus, L., or jEgialites homeyeri, 

 Br., and yE. hiaticula, L. ; one of them may be converted into 

 the other in time. It is a matter of subjective choice whether 

 or no we separate Charadrius pardela, Pall., from C. hypome- 

 lanus, Pall. In the case of living animals we need onlj'^ wait a 

 few mouths to see how, in the same individual, the one bird 

 becomes converted into the other. It is a matter of subjective 

 choice to separate Alauda semitoi'quata, Br., from A. tartarica, 

 Pall., as the one form agrees exactly with the female of the 

 other. In the above-mentioned cases I believe it is possible to 

 come to a perfectly concordant view, although at present this 

 does not exist throughout. Nature presents conditions which 

 may bi'ing about a common conception ; but she also presents 

 objective differences, which in separate individuals have, in fact, 

 caused the young, or the female, or the winter dress to be re- 



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