466 THE ZOOLOGIST. 



supplied the insect food required for her young by carrying the 

 excrements of the nestlings, as is the habit of some birds, and 

 placing them with great care on different parts of a thorn bush. 

 " Apparently she had placed them thus to attract the flies, for 

 each time she alighted on the bush she visited several, picking 

 off the flies until she had enough to take back to her young." * 

 This may surely be taken as an instance of aggressive mimicry, 

 consciously or actively pursued. According to Mr. Matthias 

 Dunn, " Some fishes have such power over their own appearance 

 that when they like they can change the colour of their skin in 

 keeping with their surroundings. I have seen Surmullets, when 

 going from the brown sand to the dark rocks, quickly change 

 from one colour to the other, and I know of about forty other 

 fishes which can do the like in more or less time."! On this 

 statement a writer has recorded that, in 1898 in the Aquarium at 

 Concarneau, in Brittany, Turbot were seen " that gradually 

 assumed the colour of the sand in which they were placed ; so 

 much so that it required a very keen eye to detect them lying at 

 the bottom of the tank."t Another writer has more recently 

 remarked, in discussing " the beautiful and protective resem- 

 blance " which- some insects " bear to their surroundings," that 

 there can be no doubt that such species " possess an inherited 

 and instinctive knowledge of this assimilation, and select such 

 places as a protection against their natural enemies." § Of course 

 the suggestion of active mimicry must not be made too absolute. 

 Thus Mr. Storrs Fox has proposed a very reasonable hypo- 



* ' Field,' July 29th, 1899, p. 227. Cf. also Dr. John Lowe, ' Zoologist,' 

 1896, pp. 1-10, as to habits of both Blackcap and Garden Warbler at 

 Teneriffe. 



f ' Contemporary Eeview,' vol. lxxvi. pp. 202-3. This observation has 

 a distinct reference to what we previously discussed as "Assimilative 

 Colouration," which cannot be divorced from the consideration of the theory 

 of " Mimicry." 



I J. G. in 'Westminster Gazette,' Aug. 10th, 1899. — A blind fish, accor- 

 ding to the observation of Pouchet, is unable to respond to the colour of its 

 surroundings." (Cf. Blake, ' Journ. Eoy. Horticultural Soc' xxiii. p. 24, 

 1899.) Prof. Henslow has given an analogous case in which the eyes of 

 Shrimps had been covered, and the result was that "these Shrimps were not 

 coloured like the normal ones, in imitation of their surroundings." (Ibid. 

 p. 28.) 



§ T. B. Jefferys, ' Entomologist,' vol. xxxi. p. 241. 



