222 Studies in the Theory of Descent. 



crescents and also the two primary nuclei coalesce, 

 producing a ring-spot which, as in Fig. 61, PL VI I., 

 segment 9, can be distinctly resolved into two 

 portions. 



It certainly cannot be denied that these facts 

 may also be theoretically interpreted in a reverse 

 sense. We might interpret the phenomena in this 

 case, as also in that of D. Zygophylli, as a gradual 

 disappearance from the front towards the hind 

 segments of ring-spots formerly present, a view 

 which could only be refuted by the ontogeny of 

 the species. I have not been fortunate enough to 

 procure eggs of D. Hippophaes, so that the younger 

 stages are unknown to me. Among my cater- 

 pillars, however, there were two in the fourth 

 stage of development, but these did not show 

 ring-spots on all the segments, as we should expect 

 on the above view ; on the contrary, no trace of 

 such spots could be seen on any of the segments 

 with the exception of the eleventh, on which 

 there was a ring-spot less perfectly developed than 

 in the last stage. 



In this fourth stage the larva of D. Hippophaes 

 is of a lighter green (Fig. 58), the subdorsal 

 yellowish with sharp boundaries, and the infra- 

 spiracular line pure white, as in the next stage. 

 The shagreening is present, but none of the 

 shagreen-dots are red or reddish, and no trace of 

 a ring-spot can be detected on the subdorsal line 

 with the exception of that on the eleventh segment. 



