NEMERTEANS 



267 



states of contraction leading to confusion. The length and breadth vary from 25 and 

 o-8 mm. to 180 and 2-8 mm., though the majority are shorter and broader than the 

 latter. 



The body is round, tapering at the posterior end. The snout is broadly acute. There 

 may be no distinction between head and body, or the head may be broader than the 

 broadest part of the body (in the smaller specimens) and two partial lateral furrows may 

 be present, almost vertical in direction, with a chevron groove behind the head. This 

 groove is complete ventrally. Sometimes the aperture of the rhynchodaeum can be seen. 

 The colour is pale pink, pinkish red, brick red, orange or light orange red, usually 

 deeper on the back and anteriorly. Sometimes the underside of the body is much paler 

 than the back. There are two groups of eyespots 

 on each side, often appearing as vague blackish 

 patches. 



Form and colour of preserved specimens. The 

 lengths and breadths of a number of specimens 

 are as follows: 51-0, 5-0 mm.; 31-0, 3-2 mm.; 

 6o-o, 4-5 mm.; 85-0, 4-5 mm.; 14-0, i-8mm.; 

 32-0, i-8 mm.; 130-0, 3-5 mm. 



The body is round in section, the head blunt 

 and the tail acute. The head is usually marked 

 off from the body by a distinct and almost 

 complete annular groove ; dorsally this groove 

 forms a wide V with the apex pointing back 

 (Fig. 44). Anterior to this there are often lateral grooves, as in Fig. 44, and sometimes 

 a median vertical groove in which can be seen the openings of the head gland and 

 rhynchodaeum. The eyes are not all visible unless the specimen is cleared. On clearing 

 two groups of brown cup-shaped eyespots can be determined on each side. The eyes 

 vary from fifty or so in each group to small numbers like seven in the anterior and four 

 in the posterior group of one side. They appear to increase with the size of the worm. 

 The anterior eyes open forwards, the posterior more to the side, and they vary in size. 

 The colour is usually bleached, but sometimes a faint general pinkish tinge is observed. 



Anatomy. The head glands open at the tip of the head. There is a main compact 

 dorsal strand which is joined by a smaller ventral strand under the vascular loop just 

 anterior to the opening of the rhynchodaeum (Fig. 45 A). The dorsal strand becomes 

 thin and scattered posteriorly and does not extend to the brain. The ventral strand 

 forms an investment to the rhynchodaeum on each side and continues back past the 

 junction with the oesophagus. It, too, disappears before the brain. 



The epithelium is very thick. In places it is thicker than basement membrane, circular 

 muscles and longitudinal muscles put together. The basement membrane itself is thick 

 and stains strongly. In the head, at about the level of the cerebral organs, there are 

 eosinophile glands in the longitudinal layer whose ducts pass through the circular layer 

 and basement membrane. These are not seen farther down the body. 



Fig. 44. Amphiporus spinosus, Burger. 

 A, ventral ; and B, dorsal surface of head. 



