438 Mr. F. Merrifield on Temperature Experiments. 
which undoubtedly influences size and vigour, and is 
generally considered also to influence markings and 
colour, offers another line in which experiments of a 
more systematic and comprehensive character than any 
yet tried would undoubtedly well repay the labour 
attendant upon them. ‘There are other natural sur- 
roundings, most potent for many purposes, the effect 
of which might usefully be tested by experiment, such 
as light and electricity and magnetism. As to light, I 
tried, in 1891, some experiments on B. cynthia and 
S. illustraria, recorded in the Trans. Ent. Soc. for 1892, 
p. 42; but, so far, with negative results. And in 1891. 
I tried some experiments with strong magnetic currents 
on some Lepidoptera in all their stages; but these 
yielded no positive result. 
Norre.—As this paper and Dr. Dixey’s, which succeeds it, con- 
tain observations on some of the same facts by two different and 
independent observers, there is necessarily some repetition, but in 
order to reduce this as much as possible, I have greatly condensed 
my own observations. 
EXpLANATION OF Prate IX. 
Fic. 1, Vanessa polychloros: pupa at 90°-95°, emerging in seven 
days. 
Fic. 2. V. polychloros: pupa about 49°, for thirty-eight days, then 
about 58° for four days, then about 85°, emerging in 
three days more. 
Fic. 3. V. polychloros: pupa at 33° for thirty-six days, then about 
49° for nine days, then about 58°, emerging in thirteen 
days more. 
Tia. 4. V. io: pupa at 33° for twenty-two days, then about 49° 
for twenty days, then about 60°, emerging in eighteen 
days more. 
