232 THE CANADIAN ENTOMOLOGIST. 



when among a hundred cases one appears where a pupa of the winter 

 generation, induced by warmth, completes its change (to prorsa) before 

 winter, this is inexplicable. It cannot be atavism which here compels it 

 in the direction of the emergence ; but we see from it that the changes in 

 the first two generations have already called forth a certain change in the 

 third, which discovers itself in this, that under favorable circumstances 

 single individuals assume the prorsa form. Or, as might also be said, the 

 alternating transmission, which carries with itself the ability to take the 

 prorsa form, as a rale remains latent in the winter generation, then with 

 single individuals turns to a continuous transmission. It is true we have 

 as yet no kind of insight into the nature of the process of inheritance, 

 and therein the incompleteness of this explanation is marked, but we 

 still know many of its outward forms of phenomena. We know that one 

 of these forms consists in this, that peculiarities in the father will appear 

 again not in the son, but in the grandson, or even further on ; that, too, 

 they may be transmitted latent. Let us suppose a peculiarity should be 

 so transmitted that it always appeared in the first, third and fifth genera 

 tions, and remained latent in the intervening ones. It would not be 

 incredible that the peculiarity should exceptionally, that is, from a cause 

 unknown to us, appear in single individuals of the second or fourth 

 generations. But this agrees with the cases mentioned in which excep- 

 tionally single individuals of the winter generation took the prorsa form, 

 only with the difference that here a cause — heat — appeared which 

 occasioned the bringing out the latent characters ; though in what way it 

 exerts this influence we are unable to say. These exceptions to the rule 

 are no objection to the theory. On the contrary, they give us a hint that 

 jrhere one prorsa generation had formed itself, the gradual insertion of a 

 second might be facilitated by the existence of the first. It is not to be 

 doubted that in the open air single individuals of the prorsa form some- 

 times emerge in September or October. But if our summer were 

 lengthened by a month or two, these could lay the foundation of a third 

 summer generation, just as a second is now an accomplished fact. 



Dorfmeister (who formerly experimented on the effect of cold on 

 pupae of butterflies) believes that he may conclude that temperature 

 exerts the greatest influence during the turning into chrysalis, but nearly 

 as much shortly after the same period ; and this conclusion may be correct 

 in so far as everything depends on whether in the beginning the formative 

 processes in the pupa turned in this or that direction, the final result of 

 which is the prorsa or levana type. When, however, one or the other 



