﻿350 J. DEWITZ — THE BEARING OF PHYSIOLOGY 



flowers of certain plants at certain fixed hours of the day. Perhaps one does not 

 go wrong in attributing this punctual transformation and behaviour of insects and 

 other animals to the relief which light gives to the tension in their tissues, as is 

 also the case with the opening and closing of flowers. That leads us to a question 

 of the highest interest, namely, of the effect of the seasons, and in that respect T 

 should like to speak of a Physiology of the Seasons, of which autumn is particularly 

 interesting. Numerous organisms, after having passed through various stages 

 of development (eggs, pupae, gemmules of sponges, spores, bulbs, buds, etc.) then 

 sink into a state of rest, and nothing, not even a raised temperature, can naturally 

 interrupt that rest, until it terminates in its normal course. But we observe 

 frequently — and many people look upon it as a freak of nature — that even late 

 in autumn some trees blossom a second time and species of insects appear as if 

 spring was approaching and not winter. 



Occasionally specimens of the grape-moth, C. amhiguella, appear in the 

 vineyards, and give rise to the fallacious hope of vineyard owners that the whole 

 of that destructive insect pest would perish through the inclement weather and 

 for want of food. I have frequently referred 14 to this subject in connection with 

 C. ambiguella (Landwirtschaftl. Jahrbiich. Bd. 36, 1907, p. 983) and have 

 ventured to express the hope that science and the inventive genius of man may 

 yet succeed in finding means and ways for postponing artificially the general 

 appearance of that most destructive insect from summer to late autumn, that is, 

 to such a time of the year when climate and atmospheric conditions disastrously 

 affect its existence. 



In some cases the normal period of rest has already been successfully reduced 

 by artificial means, The treatment of plants and flowers with ether or warm 

 water, in order to promote artificially the more rapid formation of buds and 

 flowers is well known to gardeners. Other instances concern lower animals. It 

 is generally known how, by subjecting the eggs of the silk-worm in summer to a 

 process of refrigeration the normal period of such rest is changed. Several 

 experimenters have been well aware of this peculiarity and have more closely 

 studied it, prominent amongst them being E. Duclaux (C. R. Acad. Sc. Paris, 

 1869, p 69 ; 1871, p. 73 ; 1876, p. 83). Italian investigators have since employed 

 with success acids, electricity, etc. According to Weissmann* 5 the period of rest 

 of Cladocera is considerably shortened by temporary desiccation or refrigeration. 

 Standfuss 34 succeeded in producing moths in autumn from insect pupae which 

 normally hibernate, by applying to the latter abundant humidity after they had 

 been kept for a long period in a very dry condition. When 200 to 400 pupae 

 of Satnmia were kept 7 to 10 weeks (from June to end of September) in a very 

 dry atmosphere and then thoroughly moistened a few times at short intervals, 

 about 1 per cent, of such pupae emerged, which under normal conditions would not 

 happen before the following May. 



All these methods have one point in common, namely, that they cause loss of 

 water in the tissues. Raph. Dubois, 18 who has written much about this expelling 

 of water by means of cold, ether and other anaesthetics, has applied to these 

 methods the word " atmolyse. " 



The autumn season produces also other notable effects upon insect life. 

 During autumn males appear of many insects and other arthropods which are 



