BODILY CHARACTERISTICS— INCONSPICUOUSNESS 295 



Constant Sfecial Protective Resemblance. — A good in- 

 stance on the border line between general and special resemblance 

 is afforded by some of the Sloths, which hang head downwards 

 from the branches of trees in South American forests. The harsh 

 greenish-looking fur of these creatures harmonizes very completely 

 with the moss and lichen by which they are commonly surrounded, 

 and it is very interesting to note that the hairs are grooved or 

 fluted in a peculiar way so as to afford a lodgment to a microscopic 

 green plant (alga) which, favoured by the humidity of the air, is 

 able to grow upon them. But, in addition to this arrangement 

 promoting general resemblance, there is another bringing about 

 special resemblance, in the form of a round fawn-coloured patch 

 between the shoulders, and this is the more conspicuous because 

 it has a dark margin. The effect is similar to that produced by 

 a rotten branch which has broken off short, leaving a stump with 

 a light centre constituted by the wood, and a dark margin due to 

 the fractured bark. 



Another instance among Mammals which may more properly 

 be referred to special resemblance is afforded by the Pangolin 

 {Manis), a scaly arboreal Edentate native to East Africa and 

 Southern Asia. If alarmed when climbing a tree -trunk, this 

 animal lets go with its fore-limbs, and, supporting itself by hind- 

 limbs and tail, presents an appearance quite comparable to a 

 broken branch. 



Among Birds, the Coot, Moor- Hen, and Grebes may possibly 

 be taken, though the matter is not beyond cavil, as illustrations 

 of some particular part being shaped so as to confer special 

 protective resemblance. The toes of these birds are broadened 

 out in a very curious manner, and it has been suggested that 

 this gives them a certain resemblance to the leaves of floating 

 water-plants, whereby rapacious fishes are deceived and refrain 

 from nibbline at them. Too much stress must not be laid on 

 this, however, as it may be merely a case of broadening for the 

 purpose of increased efficiency in swimming. Or possibly two 

 ends may be gained at the same time. 



There are also cases of young birds, belonging to species in 

 which the eggs are laid and hatched out in exposed situations, 

 where the colour and markings not only harmonize generally 

 with the surroundings, but also bring about a protective resem- 

 blance to a single stone when the crouching attitude is assumed 



