( 451 ) 



relating to wing-pattern only conld fnlfil what Eimer claims for them, namely that 

 " by my researches the principal traits of the trne relationship of the forms are 

 ascertained." 



We will now leave the classificatory results in Artbildung, and devote some 

 lines to a review of a few of the conclnsious relating to the origin of species. The 

 great jiersistency with which Eimer has advocated that acquired characters are 

 hereditary, that Natural Selection is of little importance in the evolution of siiecies, 

 is admirable, and it should be acknowledged with emphasis that he insisted from the 

 first to the last on variation being definite. It was Eimer's opinion that he had 

 accomplished the thorough defeat of Neo-Darwinism by showing (I) that mutation 

 proceeds only in a few definite directions, (2) that these directions depend upon the 

 constitution of the animal and the direct influence of external conditions, not on 

 Natural Selection, and (3) that experiments with heat and cold have proved the 

 direct mutating influence of external conditions. 



Whether the directions of development are in my opinion few or many, I will 

 not say ; but it strikes me that, according to Artbildung, every <i, priori possible 

 direction of the develojjment of the pattern occurs among the Butterflies ; for we 

 learn from Artbildung and Orthogenesis that new forms may originate (1) by the 

 appearance of new characters and by the modification of old ones, and that the 

 modification may take jdace (2) in a postern-anterior or antero-posterior direction, 

 (3) in an infero-superior or in a supero-inferior direction, (4) on the fore- or on the 

 hindwing, above or below, (5) in a basi-apical or in an apici-basal direction, 

 (6) progressively or retrogressively, (7) gradually or per saltum, (8) in one character 

 of a species in one direction, in another character in an opposite direction, and so on. 

 That Eimer has not always been successful in ascertaining whether the facts bear 

 out conclusions as to the " laws " of the direction of development in the evolution of 

 the pattern, and as to the causes that govern the direction of development, may be 

 seen from a few examples. The bands of F. podaUrius are said to be inclined to 

 disappear first on the upj)erside, which is in accordance with the statement 

 (I. p. 115) th&tm th.Q podaUrius group the underside shows everywhere the more 

 original condition. The only' band of the fore wing that is liable to disappearance in 

 P. podaUrius is band vii., a band that is very often mentioned and its variation 

 described in the chapter on podaUrius in Artbildung I. ; but just this band, if not 

 obliterated, is either present on the upperside and absent from the underside, or is 

 at least larger above than below. As band vii. is a band of the original pattern 

 according to Artbildung I., the upperside, not the underside, shows here the more 

 original condition of the pattern. 



A\'e are told in Artbildung II. that tiie spring form of the Central European 

 P. machaon has the phyletically older pattern, the summer brood, the Mediterranean 

 and Asiatic forms, the younger pattern, and it is also stated that xuthus originated 

 from machaon and " stands in connection with the still more modified xuthulus." 

 Now, if in /««c/wo« the summer brood is the more advanced, how then can it be 

 explained that in the species said in Artbildung to be derived from machaon the 

 winter brood (.cuthali(s) is more advanced than the summer brood {.ruth>M)? The 

 evidence brought forward for tlie contention, that the line of development of the 

 pattern was as here maintained, will not be convinciug to anybody. The reader 

 will remember that I said before that Eimer did not know tliat xuthus and xuthulus 

 stood in the relation of summer and winter form. 



31 



