452 Mr. Poulton's/itri/ier experiments upon 



the innermost recesses of the crumpled papers. In the 

 absence of comparison experiments I cannot claim that 

 this evidence proves any susceptibility ; but I will keep 

 the cocoons to place beside others obtained in later 

 experiments. 



Acronycta triclens, 1892. — A captured mature larva 

 spun a perfectly white cocoon on the muslin floor and 

 among the white pieces of paper of the last-named 

 cylinder. Small holes were gnawed in the muslin and 

 tiie pieces fixed in the cocoon. It is probable that the 

 cocoon is, in nature, entirely concealed by foreign 

 particles, and that the colour of the silk cannot be 

 adjusted. 



Orgyia pudihunda, 1892. — Two captured larvffi spun 

 light yellowish cocoons on the muslin floor and among 

 the white tissue-paper of the cylinder in light, and 

 another spun a similar cocoon among the paper frag- 

 ments and on the muslin roof of the corresponding 

 cylinder in darkness, no effect being produced by the 

 different conditions. 



The light yellow colour and slight opacity appear in 

 this species to be solely due to the larval hairs spun into 

 the wall of the cocoon. 



Had I not been disappointed by a dealer, I should 

 have again tested the larva of Sattiniia carpini during 

 the past season. I have no doubt that Mr. Bateson is 

 right in concluding from his experiments that the colour 

 of the cocoon cannot be adjusted; but I should wish, 

 before feeling absolutely certain of this, to apply what 

 I believe is the most searching test of all, viz., dark and 

 liqkt surroundings as they occur in nature, using such 

 materials as chalk, light sand, peat, &c. 



In admitting the mistake I formerly made in applying 

 the principle of colour-adjustment to certain cocoons, I 

 still think that it applies to some cocoons, and have now 

 brought forward fresh evidence in proof of this conclusion. 



In other respects, the amount of confirmation of my 

 earlier work, and of support extended to principles sug- 

 gested in it, which I have been able to bring forward in 

 the present paper, has been a source of satisfaction. 



