Concerning the modifications of structure and the instincts necessary to produce the web of the spider, Fairhurst quotes the following from Orton's _"Zoology."_ "Spiders are provided at the posterior end with two or three pairs of appendages called spinnerets, which are homologous (correspond structually) [tr. note: sic] with legs. The office of the spinnerets is to reel out the silk from the silk-glands, the tip being perforated by a myriad of little tubes through which the silk escapes in excessively fine threads. An ordinary thread, just visible to the naked eye, is the union of a thousand or more of these delicate streams of silk. These primary threads are drawn out and united by the hind legs." From this we see that two special glands, capable of secreting a soft material that can be readily drawn into the finest threads of the greatest strength, requiring no perceptible time for drying, and two to four spinnerets perforated by more than a thousand of the smallest apertures, and hind legs modified so that they can be used to draw out the web through the spinnerets, and also the instincts which enable the spider to use its web to advantage, must all have been evolved. To evolve the silk glands would have required, as for most other organs, a long period of incipiency, during which they would have been useless. We can not assume that a substance so exceptional in its character as the web of the spider could have been suddenly produced by evolution. But the glands would be useless without spinnerets. The hypothesis asks us to assume that two or three pairs of legs that were probably at one time useful for locomotion became so modified that they could perform the function of spinnerets. But in what conceivable way could locomotive legs have become so modified and pierced with more than a thousand apertures through which the web is drawn? And how could these organs serve their purpose while the complex instincts required for their functioning were only in course of development?