152 Mr. E. B. Poulton. Colour-relation behceen the [Feb. 4, 



above, p. 300.) The eggs were fertilised by a male moth bred from 

 a yellowish larva found upon S. rubra on the River Cherwell 

 August 7th, 1884, and mentioned on p. 301 of the paper quoted 

 above, as the larva in the last stage without the brownish-red spots. 

 The larva had been fed upon apple from August 10th — 18th, without 

 causing any change of colour (see pp. 302 and 303). Thus the 

 hereditary tendencies should be towards a rather strong yellowish 

 variety, if they are due to a compromise between the tendencies of 

 the two sexes. A large number of eggs were laid in June, 1885, 

 which hatched at the beginning of July, but there was great mortality 

 among the larvae in all stages, but especially when they were very 

 young. A careful examination of the few surviving larvae was made 

 on August 12th, all the others having died before the period at which 

 it was possible to make any trustworthy observations of their colour. 



1. Salix viminalis (upper side). — One larva (hatched July 2nd) 

 had been fed upon the leaves of S. viminalis, folded and sewn so that 

 only the upper side was exposed. The larva died August 10th in the 

 last stage, after failing for some time ; it was a very green inter- 

 mediate variety, and although it had very little yellow about it, the 

 contrast with larvae fed in a normal way upon the leaves of this 

 food-plant was most interesting (although the different parentage 

 must be taken into account). 



2. Salix drier ea. — Two adult larvae (hatched July 2nd) had been 

 fed upon this plant for their whole life. One was decidedly but not 

 strongly on the yellowish side of intermediate ; the other strictly 

 intermediate. By August 20th both had ceased feeding without 

 further change. 



3. Populus nigra. — Two larvae (July 3rd) had not thriven at all. 

 One was in the fourth and one in the third stage ; the former evi- 

 dently tending, towards the whitish variety, but they were too young 

 for any certain conclusions, and by August 20th both were dead, 

 without any further results. 



The review and comparison of these results is, on the whole, dis- 

 appointing. 



Salix viminalis, upper side only (No. 1). — The result of this expe- 

 riment was very interesting. The larva was frequently placed side 

 by side with others upon ordinary S. viminalis, and the difference 

 was extremely marked. I do not think that too much weight must 

 be attached to hereditary influence in producing this effect, because 

 the other sets of experiments in this series do not prove the influence 

 to be as strong as I should have expected from the colour of the 

 parent larvae. 



Salix cinerea (No. 2). — The effects compare unfavourably with 

 tbose produced by this food-plant upon the larvae of Series III (Nos. 

 11, 12, 13), for the latter were rather more strongly influenced in the 



