366 Stiidies in the Theory of Descent. 



which they now exercise, viz., terror. We are 

 certainly not so favourably circumstanced in this 

 case in knowing a species which shows the initial 

 steps of this character in its last stage of life ; but 

 in the initial steps which the second stage of certain 

 species present, we see preserved the form under 

 which the eye-spots first appeared in the phylogeny, 

 and from this we are enabled to judge with some 

 certainty of the effect which they must have 

 produced at the time. 



In the ontogeny of C. Elpenor and Porcellus 

 we see that a small curvature of the subdorsal 

 line first arises, the concavity of which becomes 

 filled with darker green, and soon afterwards with 

 black ; the upwardly curved piece of the subdorsal 

 then becomes detached and more completely 

 surrounded by black. The white fragment of the 

 subdorsal which has become separated, in the next 

 place broadens, and a black (dark) pupil appears 

 in its centre. 



Now the first rudiments of the eye-spot certainly 

 appear very insignificant in a caterpillar two 

 centimeters long, but we must not forget that in 

 the ancestors of the existing Ch<zrocampa-\2xv^ 

 this character appeared in the adult state. If we 

 conceive the curvature of the white subdorsal with 

 the underlying dark pigment to be correspondingly 

 magnified, its importance as a means of alarm can 

 scarcely be denied, particularly when we consider 

 that this marking stands on the enlarged fourth seg- 



