250 THE MECHANICAL FUNCTIONS. 



The Natural History of the spider is in many 

 points of view highly interesting, not only from the 

 great extent to which the organic developement is 

 carried, and the energy with which all the functions 

 of animal life are performed ; but also with reference 

 to the wonderful instincts displayed in the construc- 

 tion of its web, in the surprise and destruction of 

 its victims, and in the zealous guardianship of its 

 young. It would be impossible, in so brief an 

 outline as the one I am now tracing, to enlarge upon 

 so fertile a topic, without being led too far from the 

 object I have at present more particularly in view, 

 namely the developement of organization with refe- 

 rence to the organs of progressive motion. 



been assisted by the water being so nearly on the same level, I 

 poured some of it away, and placed the spider as before. It de- 

 scended by the stick, till it reached the water, and examined with its 

 two anterior feet all round ; but finding no way to escape, it returned 

 to the platform, and for some time prepared itself by forming a web, 

 with which it loosely enveloped the abdomen, by means of its hinder 

 legs. It then descended, without the least hesitation, into the 

 water, to the bottom ; when I observed the whole of the abdomen 

 covered with a web containing a bubble of air, which I presume was 

 intended for respiration, as it evidently included the spiracles. The 

 spider, enveloped in this little diving-bell, endeavoured on every side 

 to make its escape, but in vain, on account of the slipperiness of the 

 glass ; and after remaining at the bottom of the water for thirteen 

 minutes, it returned, apparently much exhausted ; for it immediately 

 coiled itself closely under the little platform, and remained afterwards 

 without motion. This property of forming for itself a reservoir of air, 

 by means of which it is preserved under water, is somewhat analogous 

 to the interesting habit of the Argyroneta, although it serves for a 

 different purpose. In the present case, it is doubtless intended to 

 enable the animal to cross the water in safety." Zoological Journal, 

 i. 283. 



