312 TEE ZOOLOGIST. 



in subtlety and power." * This argument, if it could be sub- 

 stantiated, appears to be, and has always impressed the writer, 

 as one of the most complete answers to the whole theory of the 

 protective meaning of these disguises. For if by the slow pro- 

 cess of adaptation all variations tending to these disguises were 

 increased and perpetuated by the process we express as "natural 

 selection," thus ever helping the " survival of the fittest," and 

 at the same time these changes or devevopments were equally 

 studied and more keenly detected by the attentive and hungry 

 host of insect enemies, the relations between the attackers and 

 the attacked, the eaters and the eaten, would remain much the 

 same at the commencement and end of the process. And there- 

 fore what becomes of Prof. Drummond's conception of mimicry, 

 with its " practical gain," if the enemies sought, or supposed to 

 be deceived thereby have their penetrating faculties continually 

 increasing in subtlety and power ? A moth, Agrotis cursoria, 

 not uncommon to the sand-hills on the coast of our own country, 

 " hides in the daytime in dense tufts of Ammophila arundinacea 

 (Marram grass) close to the surface of the sand, and among other 

 plants on the sea sand-hills." But "its partiality for this shelter 

 is apparently well known to the birds, as is testified by the 

 numbers of detached wings to be seen lying about."! Mr. 

 Rodway gives a similar experience in the Guiana Forest : — 

 " Invisibility is a striking characteristic of every living thing in 

 the forest. At first a stranger observes nothing but a scene of 

 desolate confusion. Later, however, he begins to distinguish 

 one tree from another, and learns where to look for a particular 

 animal. Then he wonders how he could have missed the signs 

 which now impress themselves upon his eyes."']: It is similar to 

 the extra thickness in the armour of the ironclad, which is always 

 influencing the construction of guns possessing greater pene- 

 trating power. It is like the acquired aptitude of the village 



-:■ i Tropical Africa,' 4th edit. p. 180. A similar opinion was expressed 

 by the late Fras. Pascoe: " It is not likely that animals whose lives depend 

 on their sight should be easily deceived ; though with our mostly unobservant 

 eyes a green caterpillar on a green leaf may easily escape notice " ('A Summary 

 of the Darwinian Theory of the Origin of Species,' p. 13). 



f C. G. Barrett, 'The Lepidoptera of the British Islands,' vol. iii. p. 330. 



t ' In the Guiana Forest,' p. 48. 



