126 ACQUIRED CHARACTERS sec. 



ditions, or a change in the sexual products arising by 

 correlation, to produce from such varieties absolutely separate 

 species, or to exterminate one of them. 



It is in complete accord with this hypothesis, and witli my 

 whole view of the origin of species, that the variety Bryoniae 

 is in the far north a constant sharply defined species. There 

 are other sucli cases of great interest. Anthocharis Bella 

 and Ausonia were first recognised as the summer and winter 

 form of the same species by Staudinger. They live on the 

 shores of the ^Mediterranean, extending to the middle of France. 

 In the mountains of the Yalais in the neighbourhood of the 

 Simplon Pass the winter form is alone produced. A second 

 generation is not developed in the short summer, but all the 

 pup?e remain througliout the winter. Here also, as in Bryoni?e, 

 my claims as to the effect of external conditions are com- 

 pletely fulfilled, whether Ausonia and Bryoniae, as Weismann, 

 supposes, are or are not survivals from the ice-age in the 

 localities in question. 



Polyommatus Phlseas L., the blue butterfly so common 

 with us, which ranges from Lapland to Sicily, has in Lapland 

 only one generation in the year, in Germany two. But only 

 in South Europe do these two generations differ from one 

 another, in Germany they are still similar. 



Another blue form, Lyc?ena Agestis, has a twofold season 

 variation : " The butterfly occurs in three forms : A and B 

 alternate in Germany as winter and summer form, B and C 

 are the winter and summer form in Italy. Thus the form B 

 occurs in both climates, Init appears in Germany as the 

 summer in Italy as the winter form. The German winter 

 form A is completely wanting in Italy, w^hile the Italian 

 summer form (var. Allous) does not occur in Germany." 

 Here we have plainly a little chain of modifications obviously 

 produced by climatic conditions, in which adaptation plays no 

 part, and for wliich only the views on the causes of modifica- 



