lin>'Ea:n' society of london. 35 



oP the origin o£ .1 iiiimetic fonn by means of a variation in pattern 

 so small as to deceive two extraordinarily observant naturalists, 

 an example which at the same time provides evidence that small 

 variations may be hereditary. This latter conclusion can only be 

 escaped by assuming that the constant differences between these 

 local forms are due to sonie unknown local influence and not 

 transmissible by heredity. But Dr. Eltringham has shown in the 

 memoir already referred to that both nanna and hurchcUi are only 

 two out of a long list of geographical races into which Helicon'ms 

 melpomene is split up, some of them with wide differences iu 

 ]iattern, some with small. Probalily everyone would agree that 

 the larger differences are of germinal origin and hereditary ; yet 

 large and small are all local races indistinguishable by the struc- 

 ture of the male genitalia. The onus rests upon those who would 

 put them in different categories. 



D. The OniGiisr of a Mimetic Pattern. 



The inheritance of small variations is closely connected with 

 the jjroblem of the origin of mimicry. Witiioiit sucli inheritance 

 a likeness cannot have been gradually improved, and we should 

 have before us no solution except that which assumes the sudden 

 origin of an elaborate pattern resembling in wonderful detail that 

 of some remote species. Such a solution has been proposed 

 within the last few years, and it will be well to consider some 

 of the difficulties which it encounters. 



a. A Mimetic Pattern supposed to arise suddenhj from a set of 

 Factors similar to those tvhich produced the Pattern in the Model. — 

 This suggestion was first made by Professor Punnett, who main- 

 tained that on the Mendelian view "the genera Amauris [the 

 Danaine model] and Enralia [the JNym])haline mimic] contain a 

 similar set of pattern factors, and the conditions, whatever they 

 may he, which bring about muiation in the former lead to the 

 production of a similar mutation in the latter " *. This inter- 

 pretation, although it does not carry us very far, has been 

 accepted as satislactory by some writers t. When it was pointed 

 out that the patterns of model and mimic are only superficially 

 alike and that, to name one obvious difference, the markings of 

 Amauris were hard in outline and those of the mimetic Euralia 

 {Hlipolimnas) soft J, Professor Punnett replied that "it is not 

 unreasonable to suppose that these species carry identical factors 

 for colour pattern, and that the differences by which the eye 

 distinguishes rhem are dependent upon the minuter structural 

 differences such as occur in tlie scaling. So the eye would dis- 

 tinguish belAveen a pattern printed in identical colours on a piece 



* "Mendelism," 1911, pp. 1,34. 13.5. 



t See for example tlio review by Francis 13. Sumner in Joi/rii. Philos., New- 

 York, vol. ix. i)p. l;y.)-161. 



+ Bedrock, Apr. lUlo, jip. 52. .53. 



d2 



