364 Studies in the Theory of Descent. 



eye-spots, on all the segments, in cases where it was 

 disadvantageous to the species. The fact that our 

 species of Charocamp.a have only faint indications, 

 and not a completely-developed eye-spot, on the 

 remaining segments, may perhaps be explained in 

 this manner. It is conceivable that the two pairs 

 of ocelli on the front segments are more effective as 

 a means of alarm than if the insects were provided 

 with two long rows of such markings ; but nothing 

 can be stated with certainty on this point until 

 experiments have been made with caterpillars 

 having rows of eye-spots. 



The question raised above whether the species 

 of Charocampa at present devoid of eye-spots are 

 to be expected to acquire this character in the 

 course of their further phyletic development- 

 brings with it another point, which cannot be here 

 passed over. 



If the iitility of the four kinds of markings in 

 their perfected form is demonstrated, their origina- 

 tion through natural selection is not, strictly 

 speaking, thereby proved. It must also be shown 

 that the first rudiments of these characters were 

 also of use to their possessors. The question as 

 to the utility of the " initial stages " of useful 

 characters must here be set at rest. 



In the case of markings such as longitudinal 

 and oblique stripes, it is quite evident that the 

 initial stages of these simple characters do not 

 differ greatly from the perfected marking, but 



