Instincts. 179 



to be alleged, on the part of the bird that builds these nests', 

 as evidence of a reasoning and distinguishing precaution, 

 still the question returns, whence the propensity to build 

 at all ? 



Nor does parental affection accompany generation by any 

 universal law of animal organization, if such a thing were 

 intelligible. Some animals cherish their progeny with the 

 most ardent fondness, and the most assiduous attention ; 

 others entirely neglect them ; and this distinction always 

 meets the constitution of the young animal, with respect 

 to its wants and capacities. In many, the parental care 

 extends to the young animal ; in others, as in all oviparous 

 fish, it is confined to the egg, and even, as to that, to the 

 disposal of it in its proper element. Also, as there is gen- 

 eration without parental affection, so is there parental in- 

 stinct, or what exactly resembles it, without generation. 

 In the bee tribe, the grub is nurtured neither by the father 

 nor the mother, but by the neutral bee. Probably the case 

 is the same with ants. 



I am not ignorant of the theory, which resolves instinct 

 into sensation ; which asserts, that what appears to have 

 a view and relation to the future, is^the result only of the 

 present disposition of the animal's body, and of pleasure 

 or pain experienced at the time. Thus the incubation of 

 eggs is accounted for by the pleasure which the bird is 

 supposed to receive from the pressure of the smooth con- 

 vex surface of the shells against the abdomen, or by the 

 relief, which the mild temperature of the egg may afford 

 to the heat of the lower part of the body, which is observ- 

 ed at this time to be increased beyond its usual state. This 

 present gratification is the only motive with the hen for 

 sitting upon her nest ; the hatching of the chickens is with 

 respect to her, an accidental consequence. The affection 

 of viviparous animals for their young, is in like manner 

 solved by the relief, and perhaps the pleasure, which they 

 receive from giving suck. The young animal's seeking, 

 in so many instances, the teat of its dam, is explained from 

 the sense of smell, which is attracted by the odour of the 

 milk. The salmon's urging its way up the stream of fresh 

 water rivers, is attributed to some gratification or refresh- 

 ment, which, in this particular state of the fish's body, she 

 receives from the change of element. Now of this theory 

 it may be said. 



First, that, of the cases which require solution, there are 

 few, to which it can be applied with tolerable probability : 



