230 SUPPLEMENT TO 



on the one side, and of the corresponding wall of the 

 main tube on the other. When the upper portion of 

 the main tube is thus united to the cavity the two 

 combine to form what appears like a shorty inde- 

 pendent unbranched nest. 



Now, if we fancy ourselves an insect entering the 

 nest in search either of the spider, her eggs, or young, 

 I think it is plain that^ when the lower door is in 

 this position (fig. A), we should probably walk straight 

 down to the bottom of the cavity, expecting to find 

 our prey there, and should then return by the way we 

 came, impressed with the belief that we had explored 

 the whole nest, the secret of the lower door remaining 

 undiscovered. 



Whether this imaginary case may, or may not, 

 represent what really takes place, is of course mere 

 conjecture ; but the constant occurrence of this beau- 

 tiful adaptation of the various parts to one another, 

 surel}^ 2^01^1^'' ^o the conclusion that this is no mere 

 coincidence, but rather a subtle contrivance having 

 some very definite use and meaning. 



We must admit, however, that it is difiicult to 

 conceive why, if this structure is of such great utility, 

 it should be abandoned by the oldest and largest 

 spiders. 



Among the possible answers to this question I 

 think that one of the more probable is that this 

 arrangement may have been specially devised for 

 protection against some enemy which the aged spiders 

 have ceased to fear. 



Indeed it is not unlikely that these aged spiders 

 may have come to a time of li(e when they no longer 

 lay eggs, and so do not need to keep up all the 



