220 PROCEEDINGS OF THE ACADEMY OF [1888. 



From this comparison these conclusions and inferences appear: 

 First, (1) Tunnelweavers and Citigrades have several well marked 

 common characteristics in their nesting industry that suggest a close 

 relation in spinning economy. Second, (2) the two tribes furnish 

 examples of nests that may be arranged in series of advanced indus- 

 trial skill, from a simple burrow to the highly specialized nest of 

 the Trap-door spider on one side and, on the other, to the rude door 

 or lid of Tigrina's silk-lined vestibule. Third (3), the most perfect 

 manifestation of nesting industry is found with the Tunnelweavers, 

 who are more dependent upon spinning-work for sustenance (and 

 probably i)rotection) than the Citigrades. Fourth (4), there appears 

 to be some, although no very marked relation between the animal 

 organization and the quality of the spinning work of the two tribes. 

 The greatest development in size, as well as in spinning function, 

 has been reached among the Tunnelweavers ; but most araneologists 

 would consider the Lycosids the more highly organized spiders. 

 Moreover, the Tunnelweavers are provided with long, jointed supe- 

 rior spinners (lacking in Lycosids) specially adapted for weaving 

 their more perfect nests. 



Finally, as the result of a comparative study of the nesting indus- 

 try of all the si^ider fauna, we may conclude that there is one 

 germinal or typical form of nest among all the tribes, Avhich form is 

 the tube. Around this common and rudimentary form, which has 

 been shown to be the one most natural to all animals possessing the 

 spinning function, the greatly varied and widely divergent nests of 

 spiders, — whether known as domiciles, dens, tents, tunnels, or caves, 

 —may be grouped in series of more or less modified forms. 



