210 MIMICKY IN N. AMEKICAN BUTTEEFLIES 



ists, of so large a mass of material. I shall, 

 however, be most pleased to undertake this part 

 of the investigation as regards aU specimens 

 accompanied by adequate data of space and time. 

 Such material, preserved in the Hope Depart- 

 ment, may be readily compared with the ever- 

 increasing mass of examples illustrating the same 

 principles in other parts of the world. If the 

 indications observed in a small series are stiU 

 found to hold in a large one, the growth of such 

 a feature as the orange-brown apex of the fore 

 wing in Limenitis lorquini would be demonstrated 

 by a glance at its average condition in specimens 

 from the different localities as we pass from 

 north to south. Furthermore, we might reason- 

 ably hope that a similar series collected after an 

 interval not greatly prolonged would exhibit 

 differences in average composition — the actual 

 measurable evidence of the evolution of a char- 

 acter in a species in the natural state. Even 

 though such evidence be left for our successors 

 to witness, it still remains our duty to provide 

 them with the standard by which alone they 

 will be able to detect and measure it. But I am 

 hopeful of more than this, and think it by no 

 means unlikely that a part of the reward may be 

 reaped by a single generation of workers. 



An excellent example of work done in a single 

 locality is afforded by the data obtained by 

 Mr. J. H. Cook, and summarized in the following 

 note. 



