1 (\(\ 



[iiiKiIs Jinlo)U(>loi!_ical Society of America [Vo.l III, 



]jali)us; but in none of them that I have seen, or of which I 

 have seen figures, is it as generaUzed as is the palpus of Fili statu. 

 In the palpi of the tarantulas, the genital bulb has migrated 

 to one side of the tarsus; but it is still near the tip of this seg- 

 ment of the palpus (Fig. 5). A striking feature of the bulb is 

 that it is divided into two distinct segments. The smaller 

 basal segment may be termed the basal division of the bulb 

 (Fig. 5, /;. d.). The larger segment consists of two parts: a large 

 stout part, which may be termed the middle division of the bulb 

 (Fig. .'). ;;/. d.), and a slender terminal portion, which may be 

 termed the apical division of the bulb (Fig. .'). a. d.); there is, 

 however, no distinct line between the middle and the apical 

 divisions, the one gradually merges into the other; but in the 

 more specialized palpi these two divisions are distinctly sep- 

 arated. 





III. d. 



^.d. 



^'^^.m 



r.i. d. 



II. (I 



I. d. 



Fig. .'). Tarsus of Eiirypetma. 



Fig. 6. Genital bulb if Eurypelma 

 califnniicum. 



In the articulating membrane which joins the l)ulb to the 

 tarsus, there is on one side a distinct sclerite, which can be seen 

 by removing the bulb from the alveolus (Fig. (>, pet.); this is 

 doubtless homologous with what has been termed the petiole 

 (Chamberlin '04) in more specialized ])al])i. 



The greater part of the wall of the bulb in the tarantula type 

 of palpus is very densely chitinized but there is a longitudinal 

 area on the concave side of the middle and apical divisions 

 which is comi)aratively soft (Fig. (i, p. p.); it may be that this 

 part is distended by blood pressure at the time of pairing, as 

 is the ha?matodocha in the more specialized palpi; but upon this 

 point I have no data. This soft strip may correspond to that 

 portion of the spiral type of embolus, described later, that I have 

 designated the pars peiidida. 



