Chap. II. DOUBTFUL SPECIES. 49 



be doubted would be ranked as distinct species by many 

 entomologists. Even Ireland has a few animals, now 

 generally regarded as varieties, but which have been 

 ranked as species by some zoologists. Several most 

 experienced ornithologists consider our British red 

 grouse as only a strongly-marked race of a Norwegian 

 species, whereas the greater number rank it as an 

 undoubted species peculiar to Great Britain. A wide 

 distance between the homes of two doubtful forms leads 

 many naturalists to rank both as distinct species ; but 

 what distance, it has been well asked, will suffice? if 

 that between America and Europe is ample, will that 

 between the Continent and the Azores, or Madeira, or 

 the Canaries, or Ireland, be sufficient? It must be 

 admitted that many forms, considered by highly-compe- 

 tent judges as varieties, have so perfectly the character 

 of species that they are ranked by other highly compe- 

 tent judges as good and true species. But to discuss 

 whether they are rightly called species or varieties, 

 before any definition of these terms has been generally 

 accepted, is vainly to beat the air. 



Many of the cases of strongly-marked varieties or 

 doubtful species well deserve consideration ; for several 

 interesting lines of argument, from geographical dis- 

 tribution, analogical variation, hybridism, &c, have 

 been brought to bear on the attempt to determine their 

 rank. I will here give only a single instance, — the 

 well-known one of the primrose and cowslip, or Primula 

 veris and elatior. These plants differ considerably in 

 appearance ; they have a different flavour and emit a 

 different odour ; they flower at slightly different periods ; 

 they grow in somewhat different stations ; they ascend 

 mountains to different heights ; they have different 

 geographical ranges ; and lastly, according to very 

 numerous experiments made during several years by 



D 



