ICONGL. SV. VET. AKADEMIENS HANDLINGAR. BAND. 15. NIO 7. 13 



The perigastric bodies consist of small cells more or less roundecl, the form and 

 consistency of which can be better seen by the fignres than by an}' description. 

 A nearly allied species is 



2. Mesenchytrteus mirabilis n. 



Pl. II. Fig. 3. 



The supra-oesophagial ganglion is nearly quadrangular, the two front lobes being 

 deeply separated and diverging. The ganglion is broader in front than behind (fig. 3. b). 



The receptacle is very large and turret-like. 



The tube is many times smaller than the receptacle proper, which is furnished 

 near the base with several (4 — 5) sacklike swellings or follicles for the reception of 

 the spermatozoa (Pl. II. fig. 3. c and d and Pl. III. fig. 3 u). 



The tube of the efferent duct is 6 or 8 times longer than the vesicle, but com- 

 paratively broader than that of the following species (fig. 3. e and f). 



The segmental organs have two large middle lobes. The inner duct is as large 

 as the lobes; the outer duct is somewhat shorter but broader. Sometimes the two 

 lobes may be partially grown together. The whole organ is more rounded than 

 that of the preceding species (fig. 25). 



The ovaries were arways found in the ll th and 12 th segments surrounding the 

 base of the efferent duct. 



The testes in all the specimens I dissected had a different location, viz: 



Spec. 1. had testes in the segments: 9 th , lO^TT" 1 and Ti* 1 , 13 th and 14 th . 

 » 2. » « » » » ll t h and 12 th , 13 th and 14 th . 



» 3. » » » « » ll th and 12 th . 



The perigastric bodies are of about the same shape, but somewhat larger than 

 those of the preceding species. The number of segments is about 64, all well sepa- 

 rated. The worrn in outward shape more resembles a young Lumbriculus than an En- 

 chytrceus. 



The length of the worm is 10 — 15 m. ra., the width l 1 /.» — 2 m. m. 



The spines are slightly curved and of equal length in each segment about 5, 7, 6, 5. 



Habitat. The only locality in which this species was found is Mesenkin 71° 20 

 on the right shore of the Jenissej, the individuals being only five, two of which not 

 very well developed. 



This species is altogether one of the most remarkable, but at the same time 

 one of the best defined. It is remarkable not only on account of the peculiar deve- 

 lopment of its different organs but also on account of their variability. Not two of 

 the three specimens dissected resembled each other perfectly, still they offered so many 

 characters in common that their identity is out of question. 



The general shape of the receptacle is turretlike, of a length and form some- 

 what varying. In one specimen the top was bent över (Pl. III. fig. 3 u) and half as 

 long as the whole receptacle. In another specimen the top was erect and very 



