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Show 110 l\1EANS OF EXPRESSION UnAr. IV. been specially developed to serve as an efficient soundproducing instrument, there can hardly be a doubt; for even the vertebrre included within the extremity of tho tail have been altered in shape and cohere. But thero is no greater improbability in various structures, such as the rattle of the rattle-snake,-the lateral scales of the Echis,-the neck with the included ribs of the Cobra,-ancl the whole body of the puff-adder,-having been modified for the sake of warning and frightening away their enemies, than in a bird, namely, the wonderful Secretary-hawk (Gypogeranus) having had its whole frame modified for the sake of killing snakes with impunity. It is highly probable, judging from what we have before seen, that this bird would ruffie its feathers whenever it attacked a snake ; and it is certain that the Herpestes, when it eagerly rushes to attack a snake, erects the hair all over its body, and especially that on its tail.32 We have also seen that some porcupines, when angered or alarmed at the sight of a snake, rapidly vibrate their tails, thus producing a peculiar sound by the striking together of the hollow quills. So that here both the attackers and the attacked endeavour to make themselves as dreadful as possible to each other; and both possess for this purpose specialised means, which, oddly enough, are nearly the same in some of these cases. Finally we can see that if, on the one hand, those individual snakes, which were best able to frighten away their enemies, escaped best from being devoured; and if, on the other hand, those individuals of the attacking enemy survived in larger numbers · which were the best fitted for the dangerous task of killing and devouring venomous Rnakes ;-then in .the one case as in the other, bene- 32 Mr. des Vceux, in Proc. Zool. Soc. 1871, p. 3. 111.\P. l V. IN ANIMAL~. 11 ficial variations, supposing the characters in que. tion t vary, would commonly havo been preserved thr ugh th survival of the fittest. The Drawing bacl-v ctnd p'ressure of the Ears to the Head.-. Th~ ears through their movements are highly expressive In many animals; but in some, such a. man, the higher apes, and many ruminants, they fail in this respect. A slight difference in position serve to express in the plainest manner a different state of mind~ as we may daily see in the dog; but we ar0 h re concerned only with the ears being drawn closely backwards and pressed to the head. A savag fram of mind is thus shown, but only in the case of tho animals which fight with their toeth; and the care which they take to prevent their ears being seized by their antagonists, accounts for this position. Consequently, through habit and association, whenever they feel slightly savage, or pretend in their play to be savage, their ears are drawn back. That this is tho true explanation may be iuferred from the relation which exists in very many animals between their mann r of fighting and the retraction of their ears. All the Carnivora fight with their canine teeth, and all, as far as I have observed, draw their ears back when feeling savage. This may be continually se n with dogs when fighting in earnest, and with puppies fighting in play. The movement is different from tho falling down and slight drawing back of ithe ar , when a dog feels pleased and is caressed by his mast r. The retraction of the ears may likewise be soon in kittens fighting together in their play, and in fullgrown cats when really savage, as before illu trat d in fig. 9 (p. 58). Although their ears are thus to a larg extent protected, yet they often get much torn in old |