INSTINCT, SENSATION, AND INTELLIGENCE. 2Z9 



alliance of instinct with intelligence.* So the jackdaws of Selbourn, ac- 

 cording to Mr. White, not finding a sufficiency of towers and steeples, and 

 lofty houses, on which they usually hung their nests in this pleasant village, 

 accommodated themselves to the occasion, and built them in forsaken rabbit- 

 burrows. 



The ostrich is accused of a total want of natural feeling, because she aban- 

 dons her eggs to be hatched by the heat of the sun : when incubation is ne- 

 cessary, however, the ostrich instinctively employs it, and that, too, in con- 

 junction with an intelligence which is rarely evinced by other birds. Thus 

 in Senegal, where the heat is still great, she relinquishes her eggs during the 

 day, but sits upon them through the night ; and at the Cape of Good Hope, 

 where the heat is less considerable, she sits upon them, like other birds, both 

 day and night. In like manner ducks and geese, though not renowned for 

 sagacity, cover up their eggs when they quit them, till their return to the 

 nest ; and there are few birds that do not turn and shift their eggs at different 

 periods of the tedious process of incubation, so as to give an equal degree 

 of warmth to every part. We have already observed, however, that the ac- 

 commodating power of the instinctive principle to particular circumstances, 

 which so wonderfully enables it to supply the place of reason, gives it, in 

 many instances, a striking assumption of its character. It is, hence, possi- 

 ble that one or two of the examples here noticed may be referrible to this ac- 

 commodating faculty ; but the exercise of a certain extent of reason, as a 

 distinct principle, must be admitted in several of them, in which there is not 

 only a display of design and contrivance towards the accomplishment of this 

 new object, but apparently of design and contrivance as the result of a gene- 

 ral convention and discussion of the question submitted to the tribe assembled 

 on the occasion, and whose common interest is at stake. 



Generally speaking, the principle of instinct is perfect and infallible in its 

 guidance ; there is, however, an occasional aberration, perhaps a playfulness, 

 in this as in every other part of nature. Thus the light of the candle is, by 

 flies and various other insects, mistaken for the light and warmth of the sun, 

 often to the loss of limb or even life itself. So the flesh-fly and blow-fly 

 (musca carnijica and m. vomitoria) are deceived by the smell of the carrion- 

 flower (stapelia hirsuta), and often deposite their eggs upon it instead of upon 

 putrescent meat ; in consequence of which the grubs die almost as soon as 

 hatched, for want of proper nourishment. 



In like manner we find, occasionally, a few migrating birds in countries 

 where they were never seen before, and which have evidently mistaken their 

 course. 



There are various instincts, connected, for the most part, with a singularity 

 of configuration, that are either peculiar to the birds, or altogether anomalous. 

 But they show, at least, that the great Author of nature is the lord and not the 

 slave of his own laws, and is at all times capable of producing definite effects 

 by a diversity of means. Thus the didus solitarius, or solitary dodo, in 

 general esteemed almost as stupid a bird as the ostrich, divides the labour of 

 incubation with his female, and alternately sits upon the eggs during her 

 absence. The hen of this tribe has a protuberance on each side the breast, 

 like the teat of quadrupeds. When the young of the turtle-dove are hatched, 

 and capable of receiving nutriment from the crop of the mother, the male 

 parent experiences an equal change and enlargement in this organ, secretes 

 the same nutritive material, and equally contributes to the support of its 

 nestlings. 



I have already observed that insects in general deposite their eggs in places 

 admirably suited to the future wants of the nascent larves, and then forever 

 take leave of their embryo progeny : but the forficula awncw/aWa, or common 

 ear- wig, broods over her young like a hen, and only quits them at night, 

 which is the usual period in which this genus flies in pursuit of food or 

 recreation. 



* Darw. 8vo. i. p. 241, 



