No. 2.] MENTAL POWERS OF SPIDERS. 417 



inch) to a place of safety; both then remain quiet, unless dis- 

 turbed, in which case the first spider trusts to its powers of 

 running, while the Epeirid often (but not invariably) finds its 

 best chance of safety in keeping quiet unless it is actually 

 abused ; the habit of keeping quiet also insuring the spider's 

 safe return to its web when the danger is over. There is no 

 need to call in "kataplexy" to explain the origin or develop- 

 ment of a habit which can be so easily accounted for by natural 

 selection alone. 



We hold, then, that without question Darwin's explanation 

 of the habit of lying motionless is the true one. It is the 

 result of natural selection, and has been acquired by different 

 species in different degrees, according to its usefulness in their 

 various modes of life. Thus we find it in its greatest develop- 

 ment among the comparatively sluggish Epeiridae, whereas it 

 is badly developed or lacking in the running and jumping 

 spiders, which are able, as any one who has pursued them will 

 testify, to move with astonishing rapidity. 



MISTAKES OF SPIDEI^S. 



We found spiders much less clever than we had supposed 

 them to be in regard to the recognition of their cocoons. We 

 several times endeavored to deceive them by offering a bit of 

 cotton rolled into a ball instead of their eggs, but without suc- 

 cess, so that our spiders proved a degree more intelligent than 

 the one deceived in this way by Duges ; ^ but, although they 

 were too discriminating to take the cotton, a little pith-ball led 

 them entirely astray. 



When we took the cocoon from a specimen of P. pallida, 

 and offered her in its place a pith-ball, she at first refused it, 

 although it was several times so placed that it touched her. 

 On comparing the pith-ball with the cocoon, however, we found 

 that it was three times as large. When we reduced its size, and 

 again offered it to the spider, she took it between her fakes, 

 and in a few minutes attached it to her abdomen. As far as 

 we could see, the bit of pith gave her as much satisfaction as 

 her eggs. 



We found that when the cocoons were nearly of a size one 



' Romanes' Mental Evolution in Animals, p. 382. 



