ECHIUROIDEA. 



527 



to be found in Hungary and France. They are cultivated in special ponds, 

 and take three years to attain sexual maturity. In the young stage they 

 live on the blood of insects, then on that of frogs, and only when they have 

 attained sexual maturity is a diet of warm blood necessary to them. Aulas- 

 toma Moq. Tand. , often called the horse-leech, feeds on worms and molluscs, 

 last pair of gut-caeca alone present ; A. gulo M. T. Haemopis Sav. ; H. 

 vorax M. T., the horse-leech, indigenous in Europe and N. Africa, attaches 

 itself to the interior of the pharynx of horses, cattle, and men ; jaws with 

 30 denticles. ffacmadipsa Tennent, the land-leech, in forests or damp 

 districts in or near the tropics ; Gcobddla Whitman, Australian land-leech ; 

 Leptostoma Whitman, jaws vestigial ; Limnatis M. T., 4 pairs of eyes, jaws 

 without denticles, fresh-water ; L. nilotica M. T. 

 Fain. 3. Acanthobdellidae.* Fish parasites from Siberia, on caudal and anal 



tins of Salmo salvelinus, with two 



double rows of setae on each side on 



the first 5 segments of the body (Fig. 



427). The setae are embedded in 



setigerous sacs which are provided 



with retractor muscles. Body com- 

 posed of 20 segments ; male opening 



on segment 7, female on segment 8. 



Anus dorsal to sucker (Kowalevsky). 



4 or 5 rings to one segment. Body- 



cavity spacious and incompletely 



divided by 20 segmental transverse 



septa. The nephridia are in the dis- 

 sepiments, and open between the seg- 

 ments ; internal openings not observed. 



The visceral peritoneum consists of 



chloragogen cells. The vascular system 



consists of a dorsal and ventral vessel. 



The nervous system consists of 20 



ventral ganglia, of which the first and last are composite. Testes as two 



continuous tubes in segments 6-15. Ovaries as two tubes in segments 8-13. 



The genital ducts are presumably continuous with the glands. Acanthobdella 



Grube. 



Class IV. ECHIUROIDEAf (GEPHYREA ARMATA). 



Annelida witli variable traces of segmentation in the adult ; ivitli a 

 iveU-marked preoral lobe and a pair of ventral hooked setae. 



The Echiuroidea were formerly united with the Sipunculoidea in 

 the class Gephyrea. In the present work, however, it has been 



* A. Kowalevsky, Bull. Acad. Imp. dcs Sciences St. Pctersbourg, June and 

 Nov., 1896, T. v. " 



t R. Greef, "Die Echiuren," Nov. Act. Leap. Car., 41, 1879. J. Spenge!, 

 " Die Organisation des Echiurus Pallasii," Z.f. w. Z., 34, 1880. D. C. Danielssen 

 and J. Koren, "Gephyrea," Norwegian North Atlantic Expedition, 1881. B. 

 Hatschek, " Ueb. Entwick. von Echiurus," Arb. Zool. Inst. Wicn, 3, 1881. 

 E. Selenka,," Report on the Gephyrea," Challenger Reports, vol. 13, 1885. M. 

 Rietsch, "Etude sur les Gephyriens armes," Becueil z. Suisse, 3, 1886. A. E. 

 Shipley, "Gephyrea" in Cambridge Natural History, 2, 1896. 



Fio. 427. Ventral view of anterior end of 

 Acanthobdella, showing the setae S, and 

 reserve setae Sr (after Kowalevsky). 



