( xcviii ) 



often found impossible, and that the conversion can be made 

 very thoroughly so far as many characteristics go, for example 

 as to colour and markings (or pattern). For results obtained 

 in this way, I may refer to papers contributed by me to the 

 Society's Transactions, which Dr. Dixey has done me the honour 

 to epitomize most accurately in an article in " Nature " of 

 23rd December, 1897.* 



Some observation has been made f on the distinction I have 

 drawn between "markings" (pattern) and "colouring," but I 

 do not think any one who has seen the results of my experi- 

 ments can doubt that the distinction is a real and very 

 substantial one. To speak first of the markings (pattern), a 

 striking change in these is caused by the exposure for many 

 weeks of the summer pupa of *S'. tetralunaria to a low tempera- 

 ture ; further, this change is distinct^ in the direction of (I 

 do not say it exactly repi-oduces) the pattern which the spring 

 emergence bears. It begins to show itself after about six 

 weeks of the low temperature, and becomes the prevailing 

 pattern after about eight weeks, though even after twenty 

 weeks there is an occasional reversion to the usual summer 

 pattern. 



Stcmdfuss and Fischer's experiments. 



Probably many of my hearers are conversant with the 

 wonderful results (far surpassing mine) of high and low 

 temperatures in altering the colouring and patterns of Lepi- 

 doptera, especially the Vanessids, obtained by Prof. Standfuss } 



* It may illustrate the plastic character of the summer compared with 

 tin: winter phase of 8. tetralunaria, to mention that with the winter pnpa 

 one can only alter the colouring, but with the summer pupa one can alter 

 either colouring or markings, or both. Where extreme temperatures are 

 used, some of the effects are. doubtless to be ascribed to physiologically 

 injurious conditions; and in the converse ease, where the artificial condi- 

 i inns are specially favourable to vigorous development, such as warmth com- 

 bined with moisture, the resulting imagines may be expected to attain large 

 size and great brilliancy, as they would in nature. (See Mr. Elwes, Proc. 

 Ent. Soc. for 1891, p. viii.) Length of time in feeding up (and in pupa) 



semis tn 1 onnected with the large size and strong marking of the 



winter phase of seasonal double-brooded Geomctrids. 



I Weismanii's "Neue Ycisiichr, etc.," translation byW. E. Nicholson, 

 p. 59, reprinted from "The Entomologist," January- August, 1896. 



+ A translation by E. M. Dadd, F.E.S., of Prof. Standfuss's "Synopsis 

 of Experiments to the end of 1898," appeared in "The Entomologist," 

 1900-lilOl, and lias hern reprinted. 1 have seen no translation nt Dr. 

 Fischer's papers, bu1 hop.' to have an opportunity of referring more fully 

 to the valuable re learches of these gentlemen at some future time. 



