182 Studies in the Theory of Descent. 



previously mentioned appear as dull and inter- 

 rupted dirty yellow streaks, the same dirty yellow 

 colour showing itself continuously on the sides of 

 the four front segments. Of the subdorsal line 

 only a distinct trace is now to be seen on the 

 eleventh and on the three front segments, whilst 

 on the third segment the formation of another 

 eye-spot commences to be plainly perceptible by 

 a local deposition of black (Fig. 23). This third 

 spot does not, however, become completely 

 developed, either in this or in the last stage, but 

 the subdorsal line remains continuous on the three 

 front segments. Among other changes at this 

 stage, there occurs a considerable shortening of 

 the caudal horn, which at the same time loses its 

 beautiful black and red colours and becomes 

 brownish. 



The two large eye-spots have now nearly 

 attained complete development. The kidney- 

 shaped white spot has become entirely surrounded 

 by black ; and on the brown, red, and yellow tints 

 present in this spot during the last stage, a nearly 

 black spot has been developed the pupil of the 

 eye (Fig. 33). In order to establish a definite 

 terminology for the different portions of the eye- 

 spot, I shall designate the pupil as the " nucleus," 

 the light ground on which the pupil stands as the 

 " mirror," and the black ground which surrounds 

 the mirror as the "ground-area." 



In this fifth stage the larva attains a length 



