( xxi ) 



existenca of a dominant form in each group, the other com- 

 ponents of which were capable of being arranged in a 

 descending order of resemblance to it. That was scarcely 

 borne out by the specimens. A group such as that shown 

 from Panama presented several hypertelic pairs and did not 

 support the idea that the species could be arranged in degrees 

 of adaptation towards one particular model. Whilst the 

 facts of geographical distribution afforded, in his view, 

 a real objection to the Miillerian theory, he did not look to 

 distribution alone as likely to have had a considerable share in 

 the production of these groups.* It might have had some ; 

 but their production might conceivably be due to a variety of 

 causes, and not one alone. 



He had certainly intended his remarks on hypertely to be 

 taken as a criticism of the Miillerian hypothesis. 



However effective a destructive agency might be in pro- 

 ducing change, directly it became non-selective, the resulting 

 change must stop short at the point reached ; and his 

 argument was that the process of discrimination by birds, 

 the only available agents, would be limited to the recognition 

 of a group of associated forms as an inedible whole, and being 

 superfluous if carried farther would not be exercised so as to 

 bring about such minute resemblances as were often met 

 with. As an instance, he might mention the two Brazilian 

 groups, differing in the white or yellow colour of the apical 

 spots of the forewing. To use a rough illustration, a person 

 whose object was to avoid the society of a policeman would 

 betake himself off at the first sight of the familiar uniform 

 and would not stop to decipher such minutige as the distin- 

 guishing number thereon. His view was strengthened by 

 the President's admission that in Miillerian groups there 

 apparently did not exist the same necessity for exact 

 imitation as was demanded in the case of Batesian mimics ; 

 it practically conceded his point. 



Every one who had listened to the discussion must, he 

 thought, be struck with the amount of doubt thrown on the 



'■' The objections to any explanation based on distribution alone 

 have been forcibly stated by Fritz Miiller himself. " Kosmos," 

 1882, p. 262. 



