422 H. M. KYLE [December 1899 



This includes " those individuals which live within a certain region, 

 under equal conditions, have the same habits, and stand in close blood- 

 relationship through intercrossing and reproduction." The characters 

 of these individuals will come under the laws formulated here as pro- 

 positions II. and III. 



The older systems regarded the above as the species, but in a 

 natural system the " species " is the second group. It is a certain 

 " combination " of races whose exact limitation has to be determined in 

 all particular cases. The species is but a larger " race," and may be 

 sharply marked off from or merge into the races of another species. 

 The sharper the races can be marked off from one another the clearer 

 will be the distinction between the species. 



As this paper is so short, it is hardly necessary to make any 

 summary. The endeavour has been to display the meaning and im- 

 portance of Heincke's work, and if further information is desired refer- 

 ence should be made to the original work. 



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2. Bateson, W., " Progress in the Study of Variation," Science Progress, 1897-98. 



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4. Dunckeii, G., "Die Methode der Variationstatistik," Arch. Entivickmech. Bd. viii. 



H. 1, 1899. 



5. Duncker, G., " Fr. Heincke, Natur. Geschichte des Herings," Kritisches Referat Biol. 



Centraibl. Bd. xix. 1899. 



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22. Weldon, W. F. R., "On Certain Correlated Variations in Carcinus mocnas," ibid. v. 



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24. Weldon, W. F. R., Presidential Address, Brit. Assoc. Bristol, 1898. 



