ARACHNIDA. 647 



round this till it takes the form of a cup ; it is at this 

 stage of the work that it begins to lay its eggs in the cup, 

 and not content to fill it up to the brim, it also piles up 

 a large round heap, as high as the cup is deep. Here, 

 then, is a cup full of eggs, the under half covered and pro- 

 tected by the silken sides of the cup, but the upper still 

 bare and exposed to the air and the cold. She now sets 

 to work to cover these also : the process is similar to the pre- 

 ceding, that is, she weaves a thick web of silk all round 

 them, and, instead of a cup-shaped nest, like some birds, 

 the whole partakes of the form of a ball much larger than 

 the body of the Spider. 



The feet of the Spider, one of which is represented at 

 No. 4, are curiously constructed. Each foot, when mag- 

 nified, is seen to be armed with strong horny claws, with 

 serrations on the under-surface. By this arrangement the 

 Spider is enabled to regulate the issue of its rope from the 

 spinnarets. Some have, in addition, a remarkable comb- 

 like claw, for the purpose of separating certain threads 

 which enter into the composition of their delicate webs. 



One of the most remarkable members of the family, the 

 Argyroneta aquatica, Diving Spider, weaves itself a curious 

 little bell-shaped globule, which it takes with it to the 

 bottom of the water, whither it retires to devour its prey. 

 Notwithstanding its aquatic habits, this, like the rest of 

 its order, is fitted only for aerial respiration ; it therefore 

 fills its miniature balloon with air, which it carries down 

 with it entangled amongst the hairs of its body. This 

 closely resembles the earliest diving-bells. 



Mr. Quekett recommended the following as a simple 

 method of obtaining a perfect system of tracheal tubes 

 from the larvae of insects : A small opening having been 

 made in the body, it is to be placed in strong acetic acid, 

 which softens or decomposes all the viscera : the trachea 

 must then be well washed with a syringe, and removed 

 from the body, by cutting away the connexions of the 

 main trunks with the spiracles, by means of fine-pointed 

 scissors. For mounting, they should be floated on to the 

 glass-slide, and laid out in the position best adapted for 

 displaying them. If we wish to mount them in Canada 

 balsam, they should be allowed to dry upon the slide, 



