4. As stated above the temperature influences practically all life phenomena in a similar characteristic way, _e. g._, the production of CO₂ in seeds[259] and the assimilation of CO₂ by green plants.[260] The writer would not be surprised if even the aberrations in the colour of butterflies under the influence of temperature turned out to be connected with the temperature coefficient. The experiments of Dorfmeister, Weismann, Merrifield, Standfuss, and Fischer, on seasonal dimorphism and the aberration of colour in butterflies have so often been discussed in biological literature that a short reference to them will suffice. By seasonal dimorphism is meant the fact that species may appear at different seasons of the year in a somewhat different form or colour. _Vanessa prorsa_ is the summer form, _Vanessa levana_ the winter form of the same species. By keeping the pupæ of _Vanessa prorsa_ several weeks at a temperature of from 0° to 1° Weismann succeeded in obtaining from the summer chrysalids specimens which resembled the winter variety, _Vanessa levana_. [259] Clausen, H., _Landwirtschaftl. Jahrb._, 1890, xix., 893. [260] Matthaei, G. L. C., _Trans. Philosoph. Soc._, 1904, cxcvii., 47; Blackman, F. F., _Ann. of Bot._, 1905, xix., 281. If we wish to get a clear understanding of the causes of variation in the colour and pattern of butterflies, we must direct our attention to the experiments of Fischer, who worked with more extreme temperatures than his predecessors, and found that almost identical aberrations of colour could be produced by both extremely high and extremely low temperatures. This can be seen clearly from the following tabulated results of his observations. At the head of each column the reader finds the temperature to which Fischer submitted the pupæ, and in the vertical column below are found the varieties that were produced. In the vertical column A are given the normal forms: TABLE XV