270 SCIENCE PROGRESS 



ments should alter the current practice with regard to taxonomy. 

 In other words, does the fact that Scardafella inca can be 

 modified by humidity into a form closely resembling S. ridgwayi, 

 or indeed into what may be called an ultra-ridgwayi form, 

 render it necessary that we should regard these two " species " 

 as identical ? To this Mr. Beebe replies in the negative. 



" The crucial point," he writes, "seems to be that, while we 

 should use this evidence to the utmost in unravelling the 

 intricate processes of evolution and in understanding the past 

 history of the wild-living forms, or, as we call them, species 

 and sub-species, as now defined, yet to alter our entire list of 

 species, discarding all forms which are ontogenetically inter- 

 changeable under experiment or in a new environment, by 

 analysis or synthesis as the case may be, is no more reasonable 

 than to discard a genus of living creatures because palaeontology 

 reveals more delicate gradations between it and a second living 

 group, isolated by the present conditions of life." 



On the other hand, Dr. D. S. Jordan, in an article on 

 " Geminate Species " published in the February number of the 

 American Naturalist, remarks that "the ontogenetic species — 

 groups in which many individuals are simultaneously modified 

 in the same way by like conditions of food or climate — show no 

 permanence in heredity. Such forms, however strongly marked, 

 would therefore have no permanent place in taxonomy. The 

 recent studies of Mr. Beebe on the effect of moist air in giving 

 dusky colours to birds serve to illustrate the impermanence 

 of the groups or sub-species characterised by dark shades of 

 colour in regions of heavy rainfall." 



Dr. Jordan, if I understand him rightly, thus advocates the 

 uniting of Scardafella ridgwayi with S. inca, and he would 

 also refuse to recognise the species or races which have 

 been named on the evidence of pale or dusky forms adapted 

 respectively to arid or humid climatic conditions. A revision 

 of our species and sub-species carried out on such lines would, 

 however, involve endless difficulties and confusion. 



I pass on to a notice of Mr. Beebe's second set of experiments 

 dealing with the seasonal colour-changes in birds, or, in other 

 words, the assumption by the males of many species of a 

 special nuptial plumage at the beginning of the breeding 

 season. These experiments, of which an account will be 

 found in the January number of the American Naturalist, are at 



