Penis ill Palpatores 59 



when it is exserted and the sheath turned inside out, because only in this position of the 

 sexual organs do the muscular fibres run straight. It follows that at any rate in Laniatores 

 the abdominal muscles alone must be capable of causing the exsertion of ovipositor. In 

 the case of Phalangioid.-e de Graaf considers that the stratum of longitudinal muscles 

 serves to draw ovipositor back, and for the reasons stated above in speaking of Laniatores 

 we must adopt this view- as far as the lateral portions of the stratum are concerned. 

 But we are not sure that the same function can be attributed to the middle portion of 

 this muscular layer on the dorsal as well as on the ventral side in Phalangioidaj, seeing 

 that this portion is attached anteriorly to the sheath, which fact had escaped de Graaf. 

 We entertain the same doubt with regard to the entire stratum in Nemastomatoidse and 

 in Cyphophthalmi, because as the muscular fibres are fixed to the sheath with both ends 

 it is even very probable that they may assist both in tui'ning out and in drawing in the 

 sheath at the commencement of these acts. 



The accessory glands of the sheath will be treated of below (p. 63, note) in connection 

 with the corresponding glands in the male. 



Penis exhibits in shape and structure excellent systematic characters for the sub-orders 

 as w'ell as for the four families of Palpatores. In all Palpatores it consists of two more 

 or less distinct parts, glans (c) and corpus penis (b). In Phalangiuiii and the genera most 

 nearly allied to it, such as Plati/buniis (PI. VI., figs. 14 and 15) and Acantholophus, the 

 junction of glans with corpus penis admits of considerable freedom of movement, as evidenced 

 by the fact that glans when in a state of rest is bent a good deal backwards, so that 

 the ventral surface turns upwards, whilst it is directed forward when penis is exserted. In 

 Leiobunum, Gagrella and Sclerosoma (PI. VI., figs. 16 and 17) the movability of glans with 

 regard to corpus penis is not so great as in Phalangini nobis, and accordingly glans is 

 directed forwards in these genera when at rest, as has been shown already by de Graaf 

 with regard to the first mentioned genus. In the other three families glans is directed 

 forwards when at re.st, or — where the distal portion of corjDus penis is arched upwards as in 

 Ischyropsalis (PL VI., fig. 18) — glans forms in point of direction the continuation of the arch. 

 In Trof/idus (figs. 26 and 27) the skin is rather thin at the junction between glans and 

 corpus, which must entail a certain freedom of movement between the parts. In Ischyropsalis 

 (figs. 18 and 19) and Nemastoma lugubre (fig. 21) the movability is very small and in 

 N. argenteo-lunulatum (fig. 25) the skin is so thick at the junction that movement seems 

 impossible. Glans is often equipped with spines var^dng in shape and number', which, we 

 think, act as incitamenta during copula. In all Palpatores glans terminates in a produced 

 slender tube, at the extremity of which is the orifice of the continuation of the seminal 

 duct; this tube is bent upwards, towards the dorsal side in Phalangioidse (PI. VI., fig. 15), 

 but in the other families it is bent downwards. In Nemastoma argenteo-lunulatum where 

 glans is uns^anmetrical (PI. VI., figs. 22 and 25) the tube of it turns downwards, and at 

 the same time to the right. In Iscliyropsalis we have noticed (PI. VI., fig. 19) a remarkable 

 feature, viz., that on either side of glans there is a sj^ot of not inconsiderable extent («'), 

 where the skin is quite thin so that it looks like a window-pane. 



Corpus penis offers not a little variety in Palpatores. In Trogulus it is quite straight, 



1 Lomau and de Graaf have discovered specific characters also, but it would be beyond the scope of the present pajier 

 in the more minute structural details of penis in the species to enter more fully on that subject, 

 examined by them. The same is the case with other species 



