[3] OLIGOCH^TOLOGICAL RESEARCHES. 881 



j a dense dermal vascular uet. The gastric vessel embraces the aliment- 

 ary canal at the middle of each segment; its many minute, tertiary 

 side branches form a dense gastric vascular net. 



The perigastric vessels in the sixth to tenth setigerous segments form 

 a kind of weakly pulsating heart, however without being distinctly 

 differentiated. The largest pair is found in the tenth setigerous seg- 

 ment, the smallest in the sixth segment. The perigastric vessels form- 

 ing the hearts are extremely long and relatively narrow, being thickest 

 near the dorsal vessel, and from there gradually decreasing in size to- 

 wards the ventral vessel. The blood is yellowish red. 



Nervoitu system. — The cerebral ganglion is very unlike that of Tubificiiii; 

 nor does it in fact resemble that of any other known Limicolide. Its 

 general shape is somewhat triangular, furnished with a large posterior, 

 projection. Its sides are concave, with two anterior projections towards 

 the cephalic lobe. The ventral ganglion emits one pair of nerves in each 

 segment; its swelling in each segment is inconsiderable. 



Gastric system resembles that of Tuhijicini to a great extent. The 

 cesophagus is long and narrow, extending to the eleventh segment; is 

 from here considerably elongated and forming the commencement of 

 the intestine, which is here hyaline, not furnished with hepatic cells. 

 In the fifteenth segment the canal contracts considerably, and is from 

 here to the end of the body covered with dark brown, glandular, hepatic 

 cells. 



Generative system. — Efferent duct, atrium, and penis are well character- 

 ized. The efferent duct is unusually narrow ; its interior end is gradually 

 increiisiug in size, forming a pear-shaped funnel. A bundle of sperma- 

 tozoa is often found in its opening, considerably protruding, as is the 

 case in Enchytrieidie. The atrium is crescent-shaped, cylindrical, and 

 furnislied Avith a set of about ten or more globular and well-delined 

 prostate glands, surrounding the atrium on all sides. Both atrium 

 and penis consist of two different layers. The prostate glands and also 

 the efferent duct are apparently developed from the interior one of 

 these layers. This explains why the atrium in Tubificidcv is "double," as 

 it has been described by Claparede,* Udekem and others (PL I, Fig, le). 

 This exterior coat of the atrium was originally only a continuation of 

 the oviduct, and is so yet in the younger stages of the worm. (About 

 this see further ahead in this paper.) 



The penis is large, its upper part being of somewhat the same shape 

 as the atrium. Its lower end is first somewhat swelled and afterwards 

 immediately tapering, forming a real external penis. This external part 

 of the penis is furnished with a funnel-shaped penis sheath (Fig. Ic, p. sh.). 

 But, contrary to what is the case in Tiibificini, this sheath is connected 

 with the apex of the penis. The same is the case with the penis sheath 

 in undeveloped specimens of Tuhijicini, but as the worm develops is the 

 sheath wholly separated from the apex (Fig. 18 e, d, g, h). The penis 

 consists of two layers; the interior one is a continuation of the inner- 



" Kecherches Anotomiquen, p. 23, and otlicrs. 

 H. Mis. G7 56 



