222 THE PRINCIPLES OF HEREDITY 



defined as that faculty which is concerned in the adaptation of 

 means to ends by virtue of inborn inherited mental impulses 

 and capacities for action. REASON may be defined as the 

 faculty which is concerned in the adaptation of means to ends 

 by virtue of acquired non-inherited mental impulses and 

 capacities for action. 



375. The lowest animals are without power of movement; 

 or at least we must suppose that the earliest animals had 

 not this power since it implies some degree of evolution. 

 Higher in the scale of animal life protoplasmic and reflex 

 action appears. Yet higher instincts are mingled with 

 reflexes, and in insects especially reach great perfection. 

 Still higher reason appears, and in the highest animal of all, 

 man, attains a position of commanding importance. 



376. Some instincts of animals are very remarkable. " Let 

 us follow the somewhat complex life-history of a beetle of 

 the family of the Blister-beetles or Cantharides, as we learnt 

 it first from Fabre. The female of the red-shouldered bee- 

 beetle (Sitaris humeralis) lays its eggs on the ground in the 

 neighbourhood of the underground nest of a honey-gathering 

 burrowing-bee (Anthophora). The larvae, when they emerge, 

 are agile, six-legged, and furnished with a horny head and 

 biting mouth-parts, as well as with a tail-fork for springing. 

 The little animals have at first no food-instinct, or at least 

 none manifests itself, but they run about, and as soon as 

 they see a bee of the genus Anthophora they spring upon it 

 and hide themselves in its thick, hairy coat. If they have 

 been fortunate the bee is a female, who founds a new colony 

 and builds cells, in each of which she deposits some honey 

 and lays an egg upon it. As soon as this has been done the 

 Sitaris larva leaves its hiding-place, bites the egg of the bee 

 open, and gradually eats up the contents. Then it moults, 

 and takes the form of a grub with minute feet and imperfect 

 masticating organs; the tail-fork, too, is lost, for all these 

 parts now are useless, since it can obtain liquid nourishment 

 without further change of place, from the honey in the cell, 

 in exactly the quantity necessary to its growth. Then it 

 spends the winter in a hardened pupa-like skin, and it is not 

 till the next year (the third), after another short larval stage 

 and subsequent true pupahood, that the fully-formed beetle 

 emerges. This again possesses biting mouth-parts, and eats 

 leaves, and has legs to run with and wings to fly with. 



377. " In this beetle, then, the food-instinct changes three 

 times in the course of its life ; first the egg of the bee is the 

 liberating stimulus, then the honey, and finally leaves. The 



