230 THE CANADIAN ENTOMOLOGIST. 



The author repeatedly tried the experiment of changing the winter to 

 the summer form by the application of heat, but always failed, and con- 

 cludes that it is not possible to constrain the winter generation to embrace 

 the summer form. He then goes on to state that levana has not only two 

 generations in a year, but three, and is polygoneutic (coining a word to 

 indicate the fact whether a species has one, two or more generations : 

 mono-di-poly-goneutic, from goneuo. to produce) , A winter generation 

 alternates with two summer generations, and the last of these gives as the 

 fourth generation of the year hybernating pupae, which in the next April 

 emerge as the first generation, and in the levana form. Such pupae (of 

 the fourth gen.) he many times, immediately on their reaching that stage, 

 placed in the green-house. But the result was always the same ; nearly 

 all the pupae hybernated. In one instance only did a porima appear 

 among them, all the rest being levana. But some of the butterflies 

 emerged in the autumn, after 14 days in pupa. These were always 

 prorsa except in one instance of porima. From these experiments it 

 appeared that like causes (warmth) have different effects on the different 

 generations of levana. With both the summer generations the high 

 temperature induced always the prorsa form; with the third this happened 

 but seldom and with single individuals, while the great mass kept the 

 levana form unchanged. One might say that this has its foundation in 

 the fact that the third generation has no inclination to hasten its emerging 

 under the influence of warmth, but that by a longer duration of the pupa 

 state must always come out the levana form. The cause of different 

 behavior under like influences can lie only in the constitution, the physical 

 nature, of the generation concerned, and not in outside influences. It 

 distinctly appears that cold and warmth cannot be the immediate cause 

 why a pupa emerges prorsa or levana. The explanation of the facts is 

 given as follows : The levana form is the primary original type of the 

 species. The pi'orsa form the secondary, produced by the gradual influ- 

 ence of the summer climate. Where we are able by cold to change 

 individuals of the summer generation into the winter form, this rests upon 

 a reversion to the original form, upon atavism, which, as it appears, is 

 most readily called out by cold, that is, by means of the same outside 

 influences to which the original form was exposed through a long period of 

 time, and whose continuance has preserved to this day, to the winter 

 generation, the primitive marking and color. The arising of the prorsa 

 form the author imagines to have occurred as follows : it is certain that a 

 so-called ice period existed during the diluvial period in Europe. This 



