226 Mr. J. Black wall on the Structure, Functions 



connected by the closest relations of affinity, it is, perhaps, in vain 

 to expect that it will ever be applied with much success to the esta- 

 blishment of genera. 



From remarks on the structure of the palpi to the consideration 

 of the functions they perform the transition is easy and natural. 



Many spiders employ their palpi in assisting to collect the slack 

 line which results from their operations when engaged in ascending 

 the silken filaments by which they have lowered themselves from 

 stations previously occupied, or in drawing in such as have been 

 emitted from the spinners for the purpose of facilitating a change of 

 situation in some other direction. The silk collected on these occa- 

 sions is formed into a small heap, which is either attached to some 

 fixed object, or is transferred to the maxillae, and, after having been 

 mixed with saliva and reduced in volume by repeated acts of com- 

 pression, is ultimately allowed to fall to the ground. 



In conjunction with the mandibles, the palpi are employed by 

 females of the species Dolomedes mirabilis and Dolomedesfimhriatus 

 to retain their cocoons under the sternum, in which situation those 

 spiders usually carry them wherever they move. The Lycosce also 

 avail themselves of the same parts in regaining possession of their 

 cocoons when detached from the spinners. 



Certain spiders belonging to the genus Mygale have the inferior 

 part of the tarsi furnished with a dense brush of hair-like papillae for 

 the emission of a viscous secretion, which enables them to ascend 

 bodies having smooth perpendicular surfaces. Now, as the females 

 of these species usually have the under side of the digital joint of 

 their palpi, which are remarkably long and powerful, supplied in 

 like manner with papillae, analogy would lead to the conclusion that, 

 in harmony with their organization and distribution, they also con- 

 stitute a climbing apparatus. 



Various species of SalticidcB^ to which distinctness and accuracy 

 of vision are of the utmost consequence, as they do not construct 

 snares, but capture their prey by springing suddenly upon it from a 

 distance, have the terminal joint of the palpi abundantly supplied 

 with hairs, and constantly make use of those organs as brushes to 

 remove dust, or any other extraneous matter, from the corneous coat 

 of the anterior eyes. ^ 



The palpi appear to afford direct assistance likewise to spiders in 

 general in securing their prey, in changing its position while they 

 are feeding upon it, and in restraining the action of the wings of all 

 their victims which happen to be provided with them*. 



With regard to the function exercised by the remarkable organs 

 connected with the digital joint of the palpi of male spiders there 

 exists some difference of opinion. Taking anatomy as his guide, 

 Treviranus arrived at the conclusion that the parts in question are 

 used for the purpose of excitation merely, preparatory to the actual 

 union of the sexes by means of appropriate organs situated near the 

 anterior part of the inferior region of the abdomen. This view of 



* Report of the Twelfth Meeting of the British Association for the Advancement 

 of Science, held at Manchester in 1842; Transactions of the Sections, pp. 67, 68. 



