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THE AMERICAN NATURALIST [Vol. XLII 



cally placed spirals and imperfect meshing of the hub, 

 such imperfections seem to be quite as usual in adult webs 

 so that it is rare in either of these species to find per- 

 fectly symmetrical webs. The adult spider can not be 

 said- to construct a more serviceable snare than does the 

 spiderling, for the spiderling's is really much larger in 

 diameter in proportion to the size of the body. And while 

 the adult has about twice as many spiral loops, the spider- 

 ling with his fewer loops probably secures all necessary 

 nourishment to the same extent as does his mother. Thus 

 with the growth of the spider the snare does not become 

 more serviceable as a trap. In all this excellent architec- 

 ture the young as well as the adult labors first to make 

 a scaffolding to support its weight, then lays down upon 

 this the food-gathering spiral; and it does this quite as 

 efficiently as does the adult. We might conclude that the 

 number of spiral loops becomes larger because the supply 

 of available silk has greatly increased; and that more 

 radii are added because the weight of the spider increases 

 faster than the size of the web, and because the spider 

 in all her building tests the strength of the scaffolding, 

 adding a new line wherever the structure sags. But the 

 increase in number of parts can not be ascribed to intel- 

 ligence, or memory of reiterated experience, for the 

 mother seems to continue the same instinct possessed by 

 the young and shows no peculiarity in the spinning pro- 

 cess not exhibited by the latter. The age differences of 

 the web are, accordingly, due mainly to: (1) increase in 

 the weight of the spider in combination with the instinct 

 to make the scaffolding sufficiently strong ; and increase 

 of size of the spinning organs, therefore of silk substance. 

 The spider does not exhibit learning at any stage, for it 

 constructs the first web with as much ease and certainty 

 as any later one. Tn this connection I may also mention, 

 as the result of many observations, that the spider makes 

 the first cocoon as perfectly as any subsequent cocoon; 

 and when it makes a mistake at any part of the process 

 of cocoon spinning seems unable to rectify it. 



