30 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 



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

 {C. el'uKjuai'ia, R. cratmjata, 1S86, II)." 



"The effects can not be reversed by reversiui;- the surroundings for a short time (C elhi- 

 (piaria, 11. ahrnjitaria. A. JiftaJaria). 



" AA'hen the conditions are uniform the response to environment does not necessarily destrov 

 individual variability, but the most powerful forms of environment, when applied to highly 

 sensitive species, very nearly do away with it. 



"If the environment be mixed there does not appear to be any instinctive knowledge leading 

 the larvie to rest only on appropriate ol)jects. 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 

 otiered to them. 



"The instinct of these Giomdrx i.s to rest upon twigs under any circumstances, and this is 

 probably the reason why so small a proportion of things produces so great an eti'ect {A. hi/tiihtria, 

 18S9). Contact, or at all events the closest proximity, is recjuired to effect the change. Although 

 the\' are so much more susceptible to brown surroundings when these are mixed with green, 

 there were no exceptions among 105 lai'Viv whidi, in 1889, l)ecame green among leaves and 

 shoots. 



"The effects pi'oduced on the larva; do not influence the colors of the moths (A. hetuho'iu). 



" Darkness does not produce so great an eflVct as black surroundings in strong light (^4. 

 hetularia, R. ei'atx.gafa, C. elinguaria). Overcrowding tends to produce dark \i\v\K {A. h>fii1(n'iu, 

 R. cratiegata). 



"In the case of R. cratxgata and A. hetidaria there is direct evidence of the power being 

 efficient in concealing the wild larvse. The larvse ai'e probabU' chiefly sensitive at the time when 

 they ([uit the leaves and first begin to rest on the twigs." 



VII. LIFE-HISTORY OF CERATOMIA AMYNTOR. 



{\'\-Mv XXXI V.) 



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 larviv hatched out at Brunswick, Me., early in the 

 morning of August 9. 



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

 flattened, as in the Ceratocampina\ The shell is V(>ry thin and transparent, and under a strong- 

 hand lens is seen to be minutely pitted. Length, about 1.7 mm.; breadth, 1..5 nun. 



Larra, Stage I (tig. 1. la). — Length when hatched, -i.S-.o mm., becoming at thcend of the stage 

 1:2-13 mm. Its general shape and proportions are much like those of Eac/rs inqx-riaUs, though 

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

 head is, on escaping from the pgg, a))Out twice as wide as the hinder part of the body, being 

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

 the body. 



The head and liody arc very pale, whitish, glaucous green, the head and ])ody of the same 

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

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



ol have observed that the flower-spider {Mimmena ratia) require.? at least a week or ten days to change from 

 white to yellow. This si)e(:ies is translucent and probably changes sooner than others of its family. G. Pouchet first 

 studied the faculty of adjustment of the color of shrini])S to tliat of their environment, which faculty he calls the 

 "chromatic function" and which is due to the movements under the stimulus of light of the pigment cells (chro- 

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

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

 Phvsiolugv of tlie Higher Crustacea" (Phil. Trans., vol. 196, pp. 295-388, 19U4.) 



