io88 LIFE : OUTLINES OF GENERAL BIOLOGY 



dew or bespangled with hoarfrost, are what Walt Whitman called 

 "masterpieces for the Highest". But along with our admiration 

 there all the more arises the question: How did such an intricate 

 and effective contrivance arise ? 



If the web of the Garden Spider, for instance, stood alone of its 

 kind, what an insoluble puzzle it would be, especially as it is not 

 nowadays what would be called an intelligent achievement. It is 

 now the outcome of the spinner's instinct which requires no appren- 

 ticeship or individual learning, and is an inborn capacity for doing 

 these apparently clever things. There may have been intelligence at 

 work during its long-drawn-out racial evolution, intelligence, too, in 

 testing the little improvements that emerged from generation to 

 generation. 



The method of evolution is to test all things and hold fast that 

 which is good. But nowadays, at any rate, the spider has not to 

 think over its web-making, unless there is some very peculiar 

 situation. The web-making is part of the spider's instinctive routine; 

 it is like a chain of reflex actions. Even if we say that it is suffused 

 with vague awareness and backed by endeavour, experiments prove 

 its routine nature. The spider's web illustrates hereditary skill, not 

 individual intelligence. But our question is: By what stages did it 

 arise 7 



The most primitive spiders are hunters and wanderers ; and there 

 can be no doubt that the antecedent of web-making was paying out 

 a drag-line of silk. Whenever a spider is in a situation which demands 

 careful movements, it pays out a drag-line, which often saves it 

 from tumbling. When a spider is defying gravity by creeping back 

 downwards along the roof of a room, gripping the whitewash with 

 the toothed claws at the tips of its legs, there is always the risk 

 of a flake giving way. But if that should happen, the spider has 

 usually time to touch the roof with its spinnerets and to pay out 

 a drag-line which allows it to sink down with dignity. 



Sometimes it changes its mind, so to speak, and climbs up again, 

 a feat that we have all repeatedly watched with amazement. It 

 suggests a conjurer's trick. But the present point is that the evolution 

 of the web must start from the drag-line habit. 



The primitive spider probably lived in a hole, made comfortable 

 with a lining of silk. Nothing would be more natural than an 

 accumulation of drag-lines around the mouth of the retreat. These 

 would trip up and entangle passing insects; so what began somewhat 

 unintentionally would by its utility suggest its own extension and 

 elaboration. The most primitive spiders, which have persisted almost 

 unchanged for millions of years, since the Carboniferous Age, make 

 a home consisting of "a tunnel-like hole lined with silk, with the 

 edge of the lining drawn out all round the mouth in a fringe". 



In Ms fascinating Biology of Spiders (1928), Mr. Theodore H. 



