472 STEFAN kope6 



chemical qualities as well as in its coloring. It happens that the 

 differences are not important enough to have a decisive in- 

 fluence on the hue of the insect wing. Consequently, the real 

 cause of the color of the wings of dimorphic moths, being distinct 

 for th-B two sexes, is not the difference of the blood, but the 

 difference of the substances which are present in the cells of the 

 germs of the wings. The physiological self-differentiation of the 

 corresponding cells takes place early, even before the pupation 

 of the caterpillar. In this stage the germ of the yet unformed 

 wing seems to resemble in some degree an exposed but as yet 

 undeveloped photographic plate. 



The self-differentiation of the wing of moths, as I have stated 

 it, is sufficient to interpret the known results on the castration of 

 caterpillars, which does not lead to even the slightest changes in 

 the dimorphic coloring of the wings of the adult moth (compare 

 the experiments of Oudemans, '99; Kellogg, '04; Meisenheimer, 

 '07, '09; Kopec, '08, '11, '13, and Geyer, '13). Prell ('15 a), 

 having castrated caterpillars of the moth Cosmotriche potatoria 

 L., observed, on the contrary, a much larger variability in the 

 direction of a lighter hue in the wdngs of castrated males than in 

 normal specimens. Prell does not question the negative results 

 of the experiments on the castration of moths hitherto performed, 

 and obtained chiefly on the species BombjTc mori L. and Ljrnian- 

 tria dispar L., but he believes that the results ought not to be 

 extended to all forms of moths. It is possible that further in- 

 vestigations made in this direction would lead us to distinguish 

 between those forms of moths which react and those which do not 

 react after castration by showing a change of color of the wings. 

 But the experiments hitherto made by Prell are too small in 

 number to draw any certain conclusion from them. In Prell' s 

 investigations we also miss standard experiments, such as might 

 exclude the possibility of the influence of the operation itself, 

 whether the sexual glands were removed from the insect body 

 or not. According to Prell's own words, the castrated cater- 

 pillars refused food, and they had also to be far more abundantly 

 sprinkled with water. If we bear in mind that they were sub- 

 jected to a powerful ether narcosis and that they often lost a 



