No. 570] 



SPECIES-BUIU>IX(, 



333 



range of archippus at present and our ignorance of the 

 state of the Basilarchia stock at the time of the origin of 

 the 11 mimic" make any such specific historical guess 

 hazardous. It may, however, some time be possible by ex- 

 perimental breeding to extract from this red-spotted pur- 

 ple hybrid a red-brown type similar to archippus. If the 

 Basilarchia stock wore as easily bred as Drosophila, one 

 might be very confident of accomplishing this. In any 

 event, the theory of the origin of mimicry by natural 

 selection is, in the opinion of the writer, entirely super- 

 fluous, though this celebrated monarch-viceroy case 

 should be exhaustively studied by experimental methods, 

 to determine whether natural selection now operates in 

 any degree in the matter. 



Examples of clusters of interbreeding types may be 

 drawn in large numbers from various classes of animals 

 and plants. Bateson 12 has recently called attention to the 

 interesting case of the two American flickers described 

 by Allen, 13 the eastern Colaptcs aurafus and the western 

 and Mexican C. cafer, which hybridize in the zone in 

 which their faunal areas overlap, the American grackles, 

 the golden-winged and blue-winged warblers and their 

 hybrids, Lawrence's and Brewster's warblers, and others. 



In reference to the common purple grackle, which 

 Chapman 14 regards as a hybrid between the Florida 

 grackle and the bronzed grackle, Kidgeway 15 says: 



but since so many forms now ranke.l as sub-spe,.ie> are similarly in- 

 volved I prefer, at present, to leave the matter in abeyance. 



This significant statement from a master of ornithologi- 

 cal taxonomv indicates that hvbridization among Ameri- 

 can birds is a promising subject for investigation. 



Of the occasional mutual fertility of unlike strains dif- 

 ferent enough to be classed as unquestionable species. 



