08 MONILTGASTER HOUTENII. 



absent. The setae are arranged in pairs in 4 series ; the 

 distance between the dorsal and the ventral pair is half 

 as large as that between the two ventral pairs. The setae 

 (fig. 3) are small, about 1 ra.m. long ; they are faintly curved, * 

 almost straight, with the usual thickening in the middle 

 of their length. Their distal extremity is provided with 

 small undulating lines , perhaps due to the presence of 

 narrow ribs , like in the setae of Criodrilus. At the ven- 

 tral side of the body there are two couples of fissures , 

 the first of them between the 8*^ and 9'li ring, the se- 

 cond between the ll^h and 12'h segment, situated in a 

 line with the dorsal pairs of setae ; moreover I observed 

 a pair of smaller pores on the 14^^ segment, in front of 

 the ventral setae. 



The internal anatomy (fig 1) presents several points of in- 

 terest; therefore 1 regret that the condition of the worm is in- 

 sufficient for histological study , so that many gaps will 

 appear in the description of the structure of difi'erent or- 

 gans. The pharynx is attached to the body-wall by nume- 

 rous septum-shaped muscular bands; the Q^^ — 9''i septum 

 are extraordinary thick and muscular , fitting like funnels 

 one into another. The following septa have the usual 

 structure, but beginning with the 23'^ septum, behind the 

 gizzard , they are again strongly developed. A curious fact 

 that I wish to call attention to , is the situation of the 

 septa ; these not always correspond exactly to the limit 

 between two subsequent segments. I found the 10"'' septum 

 not situated between the lO'h and 11"> ring, but fixed 

 to the body-wall in the middle of the ll'l' segment; the 

 ll'h septum lies nearly on the boundary of the i2*h and 

 131'^ segment and the 12th septum between the 13*^^ and 

 14th ring, immediately in front of the 13'h septum (see 

 the following page). In the 9'^ segment on each side of the 

 dorsal surface of the oesophagus is a kidney-shaped pouch , 

 attached by 'a mesenterial fold to the posterior side of 

 the 8th septum; each vesicle is furnished with a long, 

 slender, coiled tube, communicating with the exterior by 



JN'otes from the Leyden üMuseum, "Vol. IX. 



