624 Ll^t: : OUTLINES OF GENERAL BIOLOGY 



records of variations in the instinctive routine of the same species. 

 From the nature of the case we cannot expect them to be numerous, 

 Hke variations in inteUigence. 



When cerebral variations — say improved differentiations and inte- 

 grations — occur in predominantly instinctive types, they must, if they 

 are to count for anything, be tested andsifted in theindividual experi- 

 ence, so that we must recognise some initiative or tentative activity 

 abetting the process of racial enregistration. The neural improvement 

 or new departure is, so to speak, a particular card in the individual's 

 hereditary "hand"; whether it will add to the racial stability or not 

 depends on how the individual plays that card. This is the tenta- 

 tive side of instinct, and one of the conditions of its evolution. 



INTELLIGENCE AND INSTINCT CONTRASTED. — Many 



years ago Kay Lankester drew a clear distinction between (a) the 

 "little brain" type, reaching a climax in ants and bees, with a rich 

 repertory of instincts and very little power of educability; and (b) 

 the "big brain" type, reaching a climax in the highest Vertebrates, 

 with relatively few instincts in the strict sense but with remarkable 

 powers of learning or profiting by experience. From a different angle 

 Bergson reached the same general conclusion, that instinctive and 

 intelligent behaviour are on different hnes of evolution, each with 

 its own advantages and disadvantages. But these two great kinds 

 of behaviour do not admit of very close comparison, still less of 

 being pitted against each other. 



It is useful to dwell for a little on the contrast between instinctive 

 and intelligent behaviour. Instinctive behaviour requires no learning, 

 but intelligent behaviour is based on what the naturally nimble 

 brain learns. The newly hatched mound-bird, having struggled out 

 of the egg-shell, has to continue to struggle out of the great heap 

 of fermenting vegetable debris. If it stops to think, or through 

 fatigue, it perishes. If it continues its instinctive struggles it wins 

 its way through, and hurries into the scrub. The Yucca Moth, as 

 we have seen, makes no tentatives; how different from the song- 

 thrush with its wood-snail! 



Instinctive capacity is shared equally by all members of the 

 species of the same sex, whereas intelligent capacity varies greatly 

 from individual to individual. All female spiders of the same kind 

 make an equally perfect web. Of course one must not make a dogma 

 o; this perfection of instinct; for mistakes are sometimes made, 

 when the consecutive manipulations are very intricate. Fabre tells 

 us of the Calicurgus wasp that stings its captured spider near the 

 mouth, thereby paralysing the poison-fangs; and then, safe from 

 being bitten, drives its own poisoned weapon into a thin part of the 

 spider's cuticle between the fourth pair of legs. But it seems that 

 the j)recisi<)n of the thrust is not always jxTfect. 



