■222 ORGANIC EVOLUTION CONSIDERED 



an aquatic mode of living. If such a change took 

 place, therefore, we would be obliged to assume that it 

 occurred in a single generation, otherwise it would 

 have been a failure. That it could have thus sud- 

 denly occurred I presume that no one would claim. 



The conclusion, therefore, is that the above changes 

 could not have been produced slowly, by natural 

 selection, nor suddenly, and that, consequently, they 

 were not produced by the process of evolution. 



I see no probable method by which the modifica- 

 tions of structure and the instincts necessary to pro- 

 duce the web of the spider could have been evolved. 

 I copy 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 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, requir- 

 ing 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 



