326 Studies in the Theory of Descent. 



Papilionidtz and Noctucz. I know nothing of the 

 conditions of life and habits of these species, how- 

 ever, and without such knowledge it is impossible 

 to arrive at a complete explanation. 



With Darwin, I take an eye-spot to be " a spot 

 within a ring of another colour, like the pupil 

 within the iris," but to this central spot " concen- 

 tric zones " may be added. In the Chcerocampa 

 larvae and in Pterogon (Enotherce, in which com- 

 plete ocelli occur, there are alway three zones 

 a central spot, the pupil, or, as I have called it, 

 the " nucleus ;" then a light zone, the " mirror ;" 

 and, surrounding this again, a dark zone (generally 

 black), the " ground-area." 



As ring-spots I will consider those ocelli which 

 are without the nucleus (pupil), and which are not 

 therefore, strictly speaking, deceptive imitations 

 of an eye, but present a conspicuous light spot sur- 

 rounded by a dark zone. 



Between these two kinds of markings there is, 

 however, no sharp boundary, and morphologically 

 they can scarcely be separated. Species with 

 ring-spots sometimes have nuclei, and ocellated 

 larvae in some cases possess only a pale spot instead 

 of a dark pupil. I deal here w r ith the two kinds 

 separately, because it happens that they appear in 

 two distinct genera, in each of which they have 

 their special developmental history. Ring-spots 

 originate in a different position, and in another 

 manner than eye-spots ; but it must not, on this 



