DESCRIPTIONS OF GENERA AND SPECIES 189 



existence oi four pairs of gonads was pointed out first of all by Letdig, and confirmed 

 later by myself (69). I was able to show that these gonads are composed of two pairs 

 of testes in x and xi, and two pairs of ovaries in xii, xiii. In no other Oligochaet 

 are there more than one pair of ovaries. The ducts are interesting on account of 

 their simplicity. Oviducts can only be distinguished from sperm-ducts by their 

 position and smaller size. The funnel opens into one segment and the external 

 aperture is upon the next. The second pair of sperm-ducts is shorter than the first 

 pair, and thus offers a transition to the oviducts, which are shorter still. The 

 spermathecae are two (P- smithii) or three (P. menkeanus) pairs, in segments vii, viii, 

 and ix. They are simple pouches without diverticula of any kind. 



The number of species of this genus is at least four ; and they are all well character- 

 ized. They may be recognized as follows : — 



Setae paired Comparatively stout worm. 



P. smithii. 

 Dorsal setae longer than 



Prostomium divided by 



transverse constriction i Setae implanted 



singly 



ventral. P.filiformis. 



Ventral setae longer than 



dorsal. P. menkeanus. 



Prostomium not divided. Dorsal setae disappear posteriorly. P. emissarius. 



(i) Phreoryctes menkeanus, Hoffmeistee. 

 p. menkeanus, Hopfmeistee, Die bis jetzt bek. Art. &c. 1845, p. 40. 

 Haplotaxis menkeanus, HoFFMEisTEE, Arch, f Nat. 1843, p. 193. 

 Georyetes menkei, Sohlotthaubee, Amt. Ber. Vers, deutsch. Naturf. zu Gottingen, 

 1854, p. laa. 

 Definition. Length, 600 mm. ; diameter, 1 mm. Number of segments, more than f)00. Ventral 

 setae longer than dorsal, both implanted singly. Habitat — Europe. 

 Besides above references see Leydig (6), Vbjdovsky (24): Giaed (2), Timm. 



(2) Phreorydtes filiformis, Glapae^ide. 

 Nemodrilus filiformis, Clapaeede, M^m. Soc. Phys. Gen. 186a, p. 275. 

 Phreoryctes heydeni, Noll, Arch. f. Nat. 1874, p. 360. 

 Phreoryctes filiformis, Vejdovsky, SB. Bohm. Ges. 1875, P- '^9^- 

 (?) Georyetes lichtensteini, Sohlotthaubee, Amt. Ber. Vers, deutsch. Naturf. 

 Gottingen, 1854, p. laa. 

 Definition. Length, 140 mm.; diameter, imm.; dorsal setae longer than ventral, implanted 



singly. Habitat — Europe, 

 This species is confounded with the last by Vaillant, although both Noll and 



