150 HOW INSECTS BREATHE. 



and extract the air. from the water thus brought into contact 

 with them. 



Truth is indeed stranger than fiction. What man would 

 have imagined such a machine ? What but Almighty 

 wisdom and power could have contrived and carried out 

 these and many other means for supplying air to the internal 

 organs of animals apparently so insignificant ? 



I have endeavoured in a few instances to point out how 

 the different modifications of these organs are adapted to the 

 different habits of their possessors, but there are many, 

 very many variations, for which we cannot at present, 

 and perhaps never shall be able to account. Some of them, 

 as, for instance, the different forms of branchiae in the 

 Ephemera, we may perhaps ascribe to that tendency to 

 variety which we see so strongly in nature. Of what use 

 are the varied tints of different birds and the species of 

 insects ? Would not a much fewer number have fulfilled 

 the same purpose ? 



And in support of this theory we may observe, that where 

 man steps in and destroys many species, to increase the 

 number of individuals of a few most useful to himself, 

 these few immediately begin to vary. The chickens, ducks, 

 pigeons, oxen, cats and horses, which, in a domestic state, 

 are found of such different tints, were probably originally 

 each of one colour ; and if they revert to a wild life, they 

 have a tendency to return also again to an uniformity in this 

 respect. (See the observations of Mr. Darwin on the Oxen 

 of the Falkland Isles, in his Naturalist's Voyage, p. 192.) 



There is indeed one capital exception to this rule — the 

 sheep ; and we shall perhaps be more grateful than fanciful, 

 if we observe that, in this instance only, variety of colour 

 would diminish from the utility to man. 



I will conclude with a brief statement of the manner in 



