RV T. HAKVEY JOHNSTON AND O. w. TlEGS. 217 



is in a contracted state. The dermis of the proboscis is relatively 

 thin and has a loose texture. 



SetcB. — The setae are rather prominent chitinous structures, 

 situated ventral ly, about 2 mm. behind the mouth in large speci- 

 mens, and projecting downwards and slightly outwards in pre- 

 served animals. They vary in number from two to four, four- 

 teen out of twenty-one specimens showing two setae, three show- 

 ing each three setae, while the other four each had four. Since, 

 with one exception, it was the larger forms that had the four 

 setae, of which one pair was * always larger than the other, it 

 would appear that the smaller setae were in process of replacing 

 the larger. Each seta is a flat, blade-like structure (Plate ix., 

 fig. 3), hooked at the free end, the larger type measuring from 2 

 to 3 mm. in length, the smaller 0"7 to 08 mm. Each lies in a 

 deep setigerous sac, projecting far into the body of the worm, 

 and ending internally close beneath the oesophagus. The seti- 

 gerous sac is merely an invaginated part of the body wall, but 

 the epidermal cells at its base are considerably elongated, and in 

 longitudinal section have a fibrous appearance. The sac of each 

 smaller seta is developed independently of, but in close connec- 

 tion with, that of a larger seta 



Connected with the setae is a powerful musculature. A strong, 

 transverse muscle pad joins their internal ends, evidently serving 

 to impart to them a lateral pincer-like movement, while a number 

 of muscles, attached internally to the ends of the seta? and ex- 

 ternally to the body wall, evidently serve to move them back- 

 wards and forwards, probably at the same time acting as pro- 

 tractors. 



Ccehme. — The body cavity is well-developed, but in places is 

 more or less fully occupied on account of the great development 

 of the intestine (Plate x., fig. 9). It is lined by a delicate peri- 

 toneum. Anteriorly, in the region of the setae, it gives off two 

 inward projections between the setigerous musculature, these 

 travelling forwards on either side of the pharynx to enter the 

 proboscis, at the end of the bifurcations of which they turn 

 sharply backwards and inwards to meet one another. This 

 could be made out in serial sections. Each coelomic extension 

 was associated witli a lateral bloodvessel (Plate ix., fig.G). 



