148 THE ENTOMOLOGIST. 



c-alhum proving tbe least sensitive), so that an enormous amount 

 of material had to be sacrificed before any laws could be deduced 

 from experiments in this direction. 



On the other hand, low temperatures for even four weeks were 

 much better tolerated. These circumstances point to the con- 

 clusion that the species tested were constrained in past ages to 

 accommodate tliemselves much more to lower than to higher 

 temperatures. 



In the face of these difficulties it would have been even now 

 impossible for me to undertake the management of such a vast 

 mass of material without the faithful and intelligent help of 

 my wife. 



It is clear that these experiments are capable of being varied 

 indefinitely, and of being performed in other ways than those 

 here described on the species discussed, or on other species 

 besides these, especially those Heterocera that emerge after a 

 short pupal period, thus opening up an excellent field of work for 

 entomological study. It is also in the highest degree probable, 

 according to the results now communicated of the influence of 

 temperature on the pupa, that in the temperature-experiments 

 recorded under the previous heads of "Egg" and " Larva" the 

 influence upon the aspect of the resulting imago could be either 

 intensified, checked, or perhaps even reversed according to the 

 degree of temperature to which the pupa was finally exposed in 

 such experiments. 



In the Trans. Ent. Soc. Lond., 1893, pp. 55 -67, with pi. iv., 

 and again pp. 69 — 73, this subject is more fully treated. 



Mr. Frederic Merrifield there publishes his very careful experi- 

 ments made with different temperatures on the pupae of Pieris 

 najn, L., Polyommatus {Chrysophanus) jMoeas, L., Va7iessa ata- 

 lanta, L., and Zonosoma (Ephyra) punctaria, L. 



Mr. Merrifield has also repeatedly published very laborious 

 researches in the same subject in jjrevious volumes of the ' Trans- 

 actions,' and in the last volume (that for 1894) has added more. 

 He varied these experiments in very different ways, and I much 

 regret that extreme pressure of work precludes me from giving 

 here a more detailed account of them. 



The following, however, must be mentioned : — With respect 

 to V. atalanta, Mr. Merrifield made observations closely similar 

 to mine; but it is especially worthy of note that pupse of P. 

 phlaas and Z. p)unctaria, of which the former had lain for ten 

 weeks and the latter for three months in the refrigerator, being 

 immediately afterwards exposed to the influence of a temperature 

 of 87" — 90" F., gave rise to perfect insects almost exactly re- 

 sembling those produced by pupae of each species that had been 

 immediately exposed to these high temperatures without any 

 sojourn in the refrigerator. 



In connection with the results of Mr. Merrifield's experiments 



