BLENDED ORIGIN, OR RLASTICITY OF INSTINCT. 209 



to meet them by intelligent adjustment, wliich, if continued 

 sufficiently long and aided by oelection. would pass into true 

 instincts of building combs in new directions, of support- 

 ing combs during their construction, of carding tlireads of 

 cloth, of substituting cement for propolis, or oatmeal for 

 pollen. 



Were it necessary, other instances of the plasticity of 

 instinct could be drawn from bees and likewise from ants,* 

 but quitting now the Hymenoptera, I shall pass to other 

 animals. 



Dr. Leech gives,t on the authority of Sir J. Banks, a case 

 of a web-spinning spider wliich had lost five of its legs, and, 

 as a consequence, could only spin very imperfectly. It was 

 observed to adopt the habits of the hunting spider, which 

 does not build a web, but catches its prey by stalking. This 

 change of habit, however, was only temporary, as the spider 

 recovered its legs after moulting. But it seems evident from 

 this case that, so far as the plasticity of instinct is concerned, 

 the web-spinning spider would be ready at any time to adopt 

 the habit of hunting, if for any reason it should not be able 

 to build a web — and this even by way of sudden transition 

 in the life-time of an individual. 



Coming now to vertebrated animals, we may easily find 

 that the same principles obtain in them. And here, for the 

 sake of brevity, I shall confine myself to instances drawn 

 from the oldest, most constant, and, therefore, presumably the 

 most fixed of the instincts which vertebrated animals display, 

 viz., the maternal. 



With regard to Birds, I showed in the preceding chapter 

 that individual variations of nest-building are not uncommon. 

 AVe have now to remark that such variations, or deviations 

 from the ancestral modes, are not always the result of mere 

 caprice, but sometimes of intelligent purpose. In order to 



* See Animal Intelligence, from wliich I may specially quote the follow- 

 ing, in order to show briefly that ants quite as much as, or more than bees, 

 present a " moving harmony " in the construction of their arcliitecture : — 

 " The characteristic trait of the • uilding of ants," says Forel, " is the almost 

 complete absence of an unchanireable moiiel peculiar to each species, such as 

 is found in wasps, bees, and others. The ants know how to suit their indeed 

 little perfect work to circumstances, and to take advantage of each situation. 

 Besides, each works for itself on a given plan, and is only occasionally aided 

 by others when they understand its plan" (p. 129). 



t Transactiuns Linn. Soc., vol. xi, p. 393. This case is briefly alluded to 

 by Mr. Darwin in the Appendix. 







