310 Mr. 'Poulion 8 farther experiments upon 



It would also be interesting to continue the experiment 

 beyond hybernation. In the case of Geometra papilo- 

 naria it has been shown that the larvge are sensitive to 

 colour influences before hybernation but not after, when 

 they become dimorphic. It is improbable that this is 

 the case with B. rohoraria, in which I anticipate that the 

 susceptibility will be found to continue. 



The species is certainly highly susceptible before 

 hybernation. 



12. Experiments in 1888 and 1889 upon Geometra 

 papilionaria. 



1888. 



The experiments in 1888 were conducted upon the 

 larvae after hybernation, when it is well known to be 

 dimorphic, appearing as green and brown forms. 



The hybernated larvae hatched from one set of eggs 

 were placed in dark and green surroundings early in the 

 spring of 1888, the date being unnoted. They were sub- 

 sequently compared as follows : — 



Experiment I. 

 Dark Surroundings. 



May 22. — 6 larva;, much larger 

 than those in II. , 3 nearly adult, 2 

 green and 1 brownish ; 3 half-grown, 

 green, with brownish on back. 



May 27. — 1 green one has spun ; 

 1 is brown and the rest green ; no 

 further change occurred after this 

 date. 



June 1. — 1 green larva spun. 



June 7. 

 spun. 



The remaining larvae 



Experiment II. 

 Green Surroundings 



May 22. — 8 larv:B : 1 nearly ma- 

 ture and green ; 3 half-grown and 

 green, but more distinctly brownish 

 on back than those in I. ; 1 smaller 

 and chiefly brown. 



May 27. — 4 large and all green, 

 like those in I. ; 4 much smaller, 1 

 brown (very small), 3 brown and 

 green. 



June 1. — 1 green larva spun ; 2 

 of the small ones had become green. 



June 7. — 3 green larv* spun ; 1 

 small larva remains brown and 3 

 green. 



The results are thus negative. Other experiments I 

 have made, but not recorded, also led to negative 

 results. It is probable that the green or brown form 

 cannot be assumed by any individual as the result of 

 susceptibility to surroundings during the stages which 

 immediately precede tbat in which they become dimorphic 



