270 PSEUDACRAEA EURYTUS 



It would seem therefore that abundance of intermediates 

 as in the case of the Pseudacraeas is in favour of the 

 Darwinian explanation. But the Mendelian claims their 

 presence also to be explicable by the theory of mutations. 

 Thus in the same article in Bedrock Professor Punnett 

 discusses the various offspring of a cross between a 

 " Silky hen " and a " Brown Leghorn " cock which 

 show grades of transition, and says : " Even if a completely 

 grading series " can be put together, it does not follow 

 " that the various forms have arisen through the accumu- 

 lation of minute variations." The series intergrading 

 between the two extremes of the cock and hen " can be 

 expressed in terms of two Mendelian factors. . . . Thus 

 an appearance of continuity in variation may be brought 

 about by the interaction of a small number of definite 

 factors upon one another." And in Mendelism, p. 162, 

 Professor Punnett says: "Neither the existence of such 

 a continuous series of intermediates, nor the fact that 

 some of them may breed true to the intermediate con- 

 dition, is incompatible with the Mendelian principle of 

 segregation." 



In his book on Mimicry in Butterflies, he also says, on 

 p. 129 : "As the result of modern experimental breeding 

 work it is recognized that an intermediate form between 

 two definite varieties may be so because it is heterozygous 

 for a factor for which one variety is homozygous and 

 which is lacking in the other — because it has received 

 from only one parent what the two typical varieties 

 receive from both parents or from neither. Its germ 

 cells, however, are such as are produced by the two 

 typical forms, and the intermediate cannot be regarded 

 as a stage in the evolution of one variety from the 

 other. ... It is quite possible that the new mimetic 

 pattern appeared suddenly as a sport, and that the inter- 

 mediates arose when the new form bred with that which 

 was already in existence." 



