LINEUS. 243 



Its geographical range is extensive, since it occurs on the 

 shores of both sides of the North Atlantic, extending from 

 Greenland in the North to Madeira on the one side and 

 Florida on the other. It also occurs, though not com- 

 monly, in the Mediterranean. 



Two very distinct colour varieties are to be met with, 

 viz., reddish brown and olive green — the latter being the 

 more common. Specimens intermediate between these 

 two are also frequent. The colour is more pronounced in 

 front, and is darker on the dorsal surface than on the 

 ventral. The snout and mouth are bordered by pale 

 margins. On the head a reddish patch marks the position 

 of the brain, and a bright red colouration is also found in 

 the head slits which is said to be due to the presence of 

 haemoglobin. On the snout in front of the brain occur 

 the deeply pigmented eyes usually varying from 3 to G in 

 number on each side, though more may be present on one 

 side than on the other. 



Of the many openings on the body two may be readily 

 seen — the proboscis pore at the tip of the head, and the 

 mouth on the ventral surface just behind the brain. The 

 anus is small and terminal. Of the other openings the 

 lateral nephridial pores in the oesophageal region can only 

 be made out in sections, whilst the numerous generative 

 pores are at certain seasons visible under a lens as a row 

 of white dots on either side in the intestinal region. 



For what is known of the habits of the worm we are 

 chiefly indebted to M'Intosh, who kept them in captivity. 

 He states (in the work above cited) that "Lineus gesserensis 

 " progresses in an easy, graceful manner, with slight 

 " undulatory motions of the head, its body being marked 

 " by successive contractile waves, which proceed from 

 " before backwards. The specimens frequently herd 

 * together in the water, which they are prone to leave, and 



