LINEUS. 269 



circumstantial, should be accepted with caution until 

 confirmation has been received from other sources. 



REGENERATION. 



Though observations on the regeneration of lost parts 

 do not exist in the case of Lineus gesserensis, yet in a closely 

 allied species, Lineus sanguineus, interesting facts in this 

 connection were brought to light by M'Intosh. When 

 kept in captivity, examples of this species shew a tendency 

 to rupture into many pieces. Each of these fragments 

 may develop into a complete worm, both anterior and 

 posterior ends being formed anew. 



PARASITES. 



Like most Nemerteans, Lineus gesserensis is frequently 

 infested with Sporozoan parasites. These occur chiefly in 

 the intestinal region attached to the epithelium of the 

 alimentary canal and hanging freely into its lumen. A 

 curious large Mesozoan parasite has also been recorded 

 in this species (Rhopalura). It is found burrowing in 

 the body wall, and its presence may be recognised, 

 according to M'Intosh, " by the perforated and honey- 

 " combed appearance of the dorsum of the affected animal, 

 " whose textures seem to be the seat of the workings of a 

 " microscopic T amicus typographicus." 



SYSTEMATIC POSITION. 



The Nemerteans are divided by Burger into four orders 

 based mainly upon the number of muscle layers in the 

 body wall, and the position of the lateral nerve cords with 

 respect to these layers. Briefly these orders, with the 

 British families and genera belonging to each, are as 

 follows : — 



