ANNULOSA, OR WORMS. 



199 



worm of enormous length, which is commonly found entwining itself 

 among the roots of Algse. 1 



597. Among the animals captured by the Tow-net, the marine Zoolo- 

 gist will be not unlikely to meet with an Annelid which, although by no 

 means Microscopic in its dimensions, is an admirable subject for Micro- 

 scopic observation, owing to the extreme transparence of its entire body, 

 which is such as to render it difficult to be distinguished when swimming 

 in a glass jar, except by a very favorable light. This is the Tomopteris, 

 so named from the division of the lateral portions of its body into a suc- 

 cession of wing-like segments (Plate xxin., B), each of them carrying at 

 its extremity a pair of pinnules, by the movements of which it is rapidly 



FIG. 408. 



FIG. 409. 



Actinotrocha branchiata:a, Epi- Pilidium gyrans:A, young, showing at a the ali- 



stome or hood; 6, anus; c, stomach; d, mentary canal, and at b the rudiment of the Ne- 



cuiated tentacles; e, mouth. mertid; B, more advanced stage of the same; c, 



newly-freed Nemertid. 



propelled through the water. The full-grown animal, which measures 

 nearly an inch in length, has first a curious pair of ' frontal horns ' pro- 

 jecting laterally from the head, so as to give the animal the appearance 

 of a ' hammer-headed ' Shark; behind these there is a pair of very long 

 antennae, in each of which we distinguish a rigid bristle-like stem or seta, 

 inclosed in a soft sheath, and moved at its base by a set of muscles con- 

 tained within the lateral protuberances at the head . Behind these are 



1 See especially Leuckart and Pagenstecher's ' Untersuchungen fiber niedere 

 Seethiere,' in Muller's " Archiv," 1853, p. 569, and Balfour, op. cit., p. 165. The 

 Author has frequently met with Pilidium in Lamlash Bav. 



