532 Mr. G. T. Baker on the distribution of 



as they may have radiated into their present habitats 

 from some point further to the north. I incUne, never- 

 theless, to the beUef that the Atlantic chain extended 

 from North Africa to the Lebanon, and that the moun- 

 tains of Crete and Cyprus are surviving fragments of it." 



We are thus provided with a land route for migration 

 from Algeria to Malatia. 



Now, resuming the thread of our argument, we may 

 assume that a white or yellow Anthocharis was generally 

 dispersed in suitable localities over the whole of this 

 area. We may, I think, further assume that the then 

 dominant form was white, and that during the subsequent 

 great secular depression of temperature it was driven to 

 certain isolated points, owing to the great struggle for 

 existence consequent on the migration southward of all 

 life. Then followed the amelioration of temperature, 

 the gradual reflex movement of life, and the subsidence 

 of the Mediterranean area giving Europe her present 

 geography. 



It now becomes advantageous, if not absolutely 

 necessary, if the species is to continue to exist, for a 

 hardier form to be produced, and gradually therefore 

 the yellow form is evolved, which in time becomes, as at 

 present, the dominant race, and in the far east (N.W. 

 Punjab) entirely supplants the ancestral stock ; though 

 I must here mention that the 2 , being the last to 

 assimilate itself, has scarcely even yet completed its 

 transformation, as it is not uncommon to see an almost 

 white specimen. In Armenia we have apparently the 

 most recent emanation of the yellow form — var. Mesopo- 

 tamica — existing side by side with the whitish Penia. 

 But Penia itself appears to be in a state of transition, 

 for it is always more or less tinged with sulphur ; and 

 this forces the conclusion that Penia is in process of 

 change towards the yellow form. Again, Tomyris is 

 even more sulphurous than the preceding species, and 

 though very distinct in shape and pattern of wings, 

 inhabiting the mountains of Askhabad without any 

 contact with the yellow group, yet it does not seem 

 improbable that it may be assimilating itself in colora- 

 tion to the present dominant race. 



We now come to the two very distinct species existing 

 side by side in Algeria, viz., Pechi and Charlonia. It is 

 curious that in this country, which appears to be the 



