THE SPIDERS. 333- 



which make this kind of nest, whereas the other more com- 

 plicated forms are in each case only built by a single species. 

 Three of the accurately known species of the Temtelarice, 

 or earth spiders (Atypus picem, A. Blackwallii and Nemesia 

 cellicola), build the simplest kind, the silken-lined tunnel 

 without any covering at the mouth. As, however, Professor 

 Ausserer, in a monograph on the earth spiders, has reckoned 

 up no less than 215 species, a very wide field here remains 

 open for discovery, and it is most highly probable that there 

 are still many among them which build nests of the single 

 door cork or of some other type. 



Moggridge has seen Australian spiders' trap-doors of the 

 type of from one to two inches in diameter, and considers 

 that this type is spread over almost all the world, whereas 

 his other types have only yet been found in certain limited 

 spots. He adds, indeed, that this latter fact may change 

 with time, but does not think that so wide a diffusion of 

 them as of the simpler type will ever be sho\vn. Let this 

 be as it may, the architecture of the cylinder-building 

 spiders shows a series of gradations and transitions from 

 imperfection to greater perfection, as would be expected 

 from the universal principles of the descent and develop- 

 ment theory, and as is incompatible with the once for all 

 determined rules or forms of behavior and building-tendency 

 laid down for animals, according to the opinion of the 

 instinct philosophers. 



That the number of these transitions through the 

 described forms is not yet nearly exhausted, is not only a 

 supposition, but is actually proved by the issue of the 

 additions found published by Mr. Moggridge in the form of 

 a supplement or appendix, the year after the appearance of 

 his interesting work. We learn therein of no less than 

 three or four more new types of trap-door nests, hitherto 

 unknown in Europe, so that the whole number of these 

 types, apart from the still very imperfectly known but also 

 very noteworthy Atypus species, mounts to six or seven. 

 This variety of forms is much conditioned by the differences 

 of the species building alike, for, as already said, the 

 same species often build very different nests, while the same 

 sort of nests belongs to the most different species, but 

 depends far more, as might naturally be expected, on the 

 variety of outside circumstances and life conditions. In 



