1903.] NATURAL SCIENXES OF PHILADELPHIA. 135 



From these data we may conclude: 



(1) That the time duration of a copulation varies from a second, 

 or a few seconds, to as much as 36 hours. When the copulation is 

 very brief it is probably frequently repeated many times, a number 

 of times in quick succession (as certain Epeirids), or repeated a number 

 of times on successive days (cf. my gbservations on Theridium tepi- 

 dariorum). When it is of some hours in duration, the female fre- 

 quently, but not always, kills the male at its conclusion (certain 

 Lycosids and Agalenids). 



(2) That the simultaneous insertion of both male palpi in the epi- 

 gynum is unusual (Pholcus, certain Theridiids). Most frequently 

 either (a) only one palpus is used during the act, or (6) the palpi are 

 alternated ; sometimes the same male may use only one palpus during 

 one copulation, and both palpi during another {Dictyna volupis, 

 Xysticus stomachosus) . When the palpi are alternated, either (a) one 

 of them may be used (continuously or with successive insertions) 

 during the first half of the copulation, and the other palpus for the 

 second half; or (6) the palpi may be frequently alternated, a strict 

 alternation of right and left after each insertion, or else one may l^e 

 inserted a mmiber of times before the other is used. 



(3) That in all cases described in sufficient detail there has been 

 noted the appearance, during insertion in the epigynum, of an evagi- 

 nated, swollen sac connected with the palpal organ; the organ is not 

 withdrawn from the epigynum until this sac collapses; this sac may 

 expand and contract rhythmically in long insertions. After the with- 

 drawal of a palpus from the epigynal orifice, the male works the palpal 

 organ between his chelicera — apparently to moisten it, as has been 

 suggested by one observer. 



(4) That within a species there is to be found considerable individ- 

 ual variations in the details of copulation. 



(5) That a particular araneid family, as at present defined, may 

 contain species which differ c^uite markedly in the details of their 

 copulation : the Epeiridcc are an example. 



The Sperm-induction, and the Origin of the Araneid Mode of Copu- 

 lation. — In the section entitled "History of Our Knowledge" all the 

 known cases of sperm-induction are mentioned. In all these cases 

 the male deposits a minute drop of semen upon a portion of web. and 

 takes up this drop into his palpal organs by applying the latter to it. 

 then shaking them in the air. There appear, however, to be some 

 difference in the details in different species. Thus the male sometimes 

 spins a special small sheet or bridge over which he stands, and on 



