206 THE FOUNDATIONS OF ZOOLOGY 



theory of natural selection alone cannot conceivably explain. In- 

 deed, it is not too much," says he, "to say that most of the facts 

 are such as directly to contradict the latter theory in its application 

 to them. I have endeavored," he says, " to show that we have a 

 large class of such cases in the domain of reflex action, and shall 

 next endeavor to show that there is another large class in the 

 domain of instinct. . . . 



" If instinct be hereditary habit, i.e. if it comprises an element 

 of transmitted experience, we at once," says Romanes, " find a 

 complete explanation of many cases of the display of instinct which 

 otherwise remain inexplicable. In all cases where instincts become 

 complex and refined, we seem almost compelled to accept the view 

 that their origin is to be sought in consciously intelligent adjust- 

 ments on the part of ancestors. 



" Thus, to give only one example, a species of Sphex preys upon 

 caterpillars which it stings in their nerve-centres for the purpose 

 of paralyzing, without killing them. The victims, when thus ren- 

 dered motionless, are then buried with the eggs of the Sphex, in 

 order to serve as food for her larvae which subsequently develop 

 from these eggs. Now, in order to paralyze a caterpillar, the 

 Sphex has to sting it successively in nine minute and particular 

 points along the ventral surface of the animal — and this the Sphex 

 unerringly does, to the exclusion of all other points of the cater- 

 pillar's anatomy. Well," says Romanes, "such being the fact, 

 it is conceivable enough that the ancestors of the Sphex, being, 

 like many other hymenopterous insects, highly intelligent, should 

 have observed that on stinging caterpillars in these particular spots 

 a greater amount of effect was produced than could be produced 

 by stinging them anywhere else ; and therefore that they habit- 

 ually stung the caterpillars in these places only, till, in course of 

 time, this originally intelligent habit became by heredity instinc- 

 tive. But now, on the other hand, if we exclude the possibility 

 of this explanation, it appears to me incredible that such an 

 instinct should ever have been evolved at all ; for it appears to 

 me incredible that natural selection unaided by originally intelligent 

 action could ever have developed such an instinct out of merely 

 fortuitous variations — there being, by the hypothesis, nothing to 

 determine variations of an insect's mind in the direction of stinging 



