SEASONAL DIMORPHISM OF LEPIDOPTERA. 37 



the wings (Fliigelanlagen) in the pupa and the germ in its repro- 

 ductive cells, and that in both elements were contained, which 

 were altered thereby in a similar way. 



It appears to me, that this case favours to no small extent the 

 assumption made by me, according to which the germ contains 

 preformed determining factors (Bestimmungsstucke) of the indi- 

 vidual elements, which later on compose the body — ** determi- 

 nants." On this supposition the behaviour of phloeas is explained 

 simply, as I have already shown elsewhere. These determinants, 

 which determine the various scales of the wing, are found in the 

 germ-plasm of the reproductive cells, and in the rudiments of 

 the wings of the pupa ; and it is easy to assume, that they are 

 struck by the heat in both places, and influenced in a similar 

 way, though not to an equal extent. We must conclude that the 

 intensity of the modification is unequal, from the fact, that in all 

 the known southern colonies of eleus the spring form is still red- 

 gold. The effect on the scale- determinants in question of the 

 germ-plasm must consequently be a very slow one, and the 

 modification, which is induced by heat is not such a one, as 

 leads under every condition to the formation of black scales, but 

 only of such a kind, that the formation of black scales takes 

 place more readily, and also, indeed, at a lesser heat. In this 

 way it can be understood, that red-gold phloeas still, indeed, fly in 

 the Neapolitan spring, but that although, at a lesser heat (the 

 room temperature of the German summer), many specimens of 

 eleus arise from pupae of Neapolitan origin. 



D. Comparison of the results obtained with those of Merrifield. 



The excellent English entomologist, F. Merrifield,* has made 

 a series of experiments with Chrysophanus phloeas, which I will 

 recapitulate here. They are in a gratifying agreement with 

 my own. 



Females of phloeas captured in England laid eggs, from 

 which 70 pupae were reared. One portion of these were kept at 

 from 27-30° C, and produced specimens with large black spots, 

 and in most cases with a slight black powdering of the fore 

 wings ; the red band of the hind wings was narrow and strongly 

 dentate. The other portion of the pupae was placed on ice, i. e. 

 kept for 10 weeks at 4° C, then for 5 weeks at 13° C. Half of 

 the butterflies were crippled or died before emergence, but those 

 which emerged were of a bright golden yellow colour, with small 

 black spots and a broad red band on the hind wings, from which 

 red lines are often continued even up the veins (just as with 

 some of my iced Neapolitan specimens) . 



* F. Merrifield (" The Effects of Temperature in the Pupal Stage on the 

 Colourmg of Pieris napi, Vanessa atalanta, Chrysophanus phloeas, «&c.") in 

 Trans. Ent. See. Lond. 1893, p. 55. 



