30 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 



"When carefully watched for, the changes are sometimes seen to occur quite suddenly 

 {C. elinguaria, R. cratxgata, 1886, 11)/' 



"The effects can not be reversed by reversino- the surroundings for a short time {('. elin- 

 guaria, H. ahniptaria, A. IjetuJaria). 



"AVhen the conditions are uniform the response to environment does not necessarily destroy 

 individual variabilit}', but the most powerful forms of environment, when applied to highlj' 

 sensitive species, very nearly do away with it. 



"If the environment be mixed there does not appear to be an\' instinctive knowledge leading 

 the larvie to rest only on appropriate objects. Thus, if they have become green and are beyond 

 the power of change, they will nevertheless rest on brown twigs in preference to leaves, if 

 offered to them. 



"The instinct of these Geotnetree is to rest upon twigs under any circumstances, and this is 

 probably tiie reason why so small a proportion of things produces so great an effect {A. hetularia, 

 1889). Contact, or at all events the closest proximity', is required to effect the change. Although 

 they are so much more susceptible to brown surroundings when these are mixed with green, 

 there were no exceptions among 105 larvie which, in 1889, became green among leaves and 

 shoots. 



"The effects produced on the larvie do not inffuence the -colors of the moths (^4. hefidnria). 



" Darkness does not produce so great an effect as V)]ack surroundings in strong light (^4. 

 hetularia, JR. cratsegata, C. elinguaria). Overcrowding tends to produce dark larv;e (^4. liefularia, 

 R. cmtiegata). 



"In the case of B. cmtiegata and .1. Irtularia there is direct evidence of the power being 

 efficient in concealing the wild larvs. The larvre are probably chietiy sensitive at the time when 

 they quit the leaves and first begin to rest on the twigs.'' 



VII. LIFE-HISTORY OF CERATOMIA AMYNTOR. 



(Piatt- XXXIV.) 



The eggs were kindly sent me from Brandon, Vt., by Miss Caroline G. Soule. They were 

 deposited on the night of July 31, and the larva? hatched out at Brunswick, Me., early in the 

 morning of August 9. 



Jlgg. — Large, oval, though nearly spherical, being but little longer than thick; it is not 

 flattened, as in the Ceratocampinw. The shell is veiy thin and transparent, and under a strong 

 hand lens is seen to be minutel}' pitted. Length, about 1.7 nun.; breadth, 1.5 nmi. 



Larva, Stage I {Hg. 1, la). — Length when hatched, -1.5-5 mm., becoming at the end of the stage 

 12-13 mm. Its general shape and proportions are much like those of Eacles ■imj)e?'iaUs, though 

 slenderer, and the close similarity in the shape of the anal legs aid in the resemblance. The 

 head is. on escaping from the egg. about twice as wide as the hinder part of the body, being 

 1.5 mm. wide; toward the end of the stage, after the Ijodv is tilled out, it is no wider than 

 the body. 



The head and body are very pale, whitish, glaucous gieen, the head and body of the same 

 hue, the latter at tirst with no definite markings. The head is smooth, with no traces of ffne, 

 short spinules; the trunk segments are also smooth, with no secondary spinules. 



«I have observed that the flower-spider (Mi.'niiiiena vatla) requires at least a week or ten da3-s to change from 

 ■white to yellow. This species is translucent and probably changes sooner than others of its family. U. Pouchet lirst 

 studied the faculty of adjustment of the color of shrimps to that of their environment, which faculty he calls the 

 "chromatic function" and which is cUie to the movements under the stimulus of light of tlie jiigment cells (chro- 

 matoijhores). He found that in the turbot the ccilor changes were only developed after the lapse of several days. 

 Very full and novel results have been obtained by Keeble and Gamble in their valuable work entitled "The Colour 

 Physiology of the Higher Crustacea" (Phil. Trans., vol. 19»i, pp. 295-388, 19114.) 



