INTRODUCTION. XI. 



simple, and no larger than the next joint, if so largo, is of a 

 tumid form, and when the spider becomes adult, i.e., at its last 

 moult, it developes into a more or less oval, sometimes very large, 

 and generally concave, somewhat spoon-like joint ; in the hollow, 

 or to the under side of this joint, is fixed a curious structure, 

 consisting of a corneous bulb, spines, processes, and lobes ; 

 sometimes thoir form is very simple, as in the Theraphosides, 

 Dysderides, and some others (pi. ii., figs. \c, If., and 6a., and pi. 

 i., fig. 15c) ; but at other times it is very complex (pi. i., fig. 

 14c), and notably so in many spocies of Linyphia, as well as in 

 somo other genera. To this structure is given the name of 

 palpal organs ; they are, in fact, the extornal instruments by 

 which the fecundation of the female spider is effected. The 

 male spider (in a manner somewhat analogous to the deposition 

 of the milt by the male fish) drops the fecundating fluid out of 

 the socreting organs (which are situated beneath the fore part of 

 tho abdomen) upon a line of its web, or possibly on a leaf, or on 

 some other substance. It then immediately imbibes or draws the 

 fluid into the bulbous portion of tho palpal organs by means of 

 an appropriate duct, whose orifice is situated at the end of one 

 of these prominent processes ; through this it is again, subse- 

 quently, injected into tho female organs, which are furnished with 

 receptacles — Spermathocra — for its retention for some days, or 

 perhaps weeks, until required for use. In some instances tho 

 male spider probably imbibes the fecundating fluid into the 

 palpal organs directly from the secreting vessels, but this has 

 not yet been actually observed. 



The variety in the form of the spines and processes, and in the 

 structure generally of the palpal organs, is apparontly without 

 limit; and thence we obtain one of the most useful, and 

 Unfailing characters for the distinction of species. Other 

 j oints of the palpi also frequently present differences, and apparent 

 eccentricities of structure. This is chiefly noticeable in respect 

 to the radial joint, which is often furnished with variously 

 formed spines and projections, or, as they are usually called, 

 apophyses (pi. i., fig. 15J). These are also most important for the 



