LINEUS. 251 



" a Eunemertes neesi of quite 20 cm. length. Some little 

 " time after I was astonished to find the Micrura busily 

 " engaged in swallowing the Eunemertes. The posterior 

 44 one-fifth of the latter had already disappeared into the 

 " mouth of the former when I noticed them, and still the 

 " assailant was struggling to gulp down more of its prey. 

 " In the meantime the victim glided round the dish, 

 " apparently not suffering the slightest inconvenience 

 "from the attack upon its posterior extremity. 

 44 Ultimately both attacker and attacked became quiescent, 

 44 the former having become more than twice its previous 

 4 ' girth. The portion of the Eunemertes in the gut of the 

 " Micrura still remained in continuity with the rest of 

 44 the body, though apparently undergoing digestion." 

 Possibly the food is digested and absorbed and the excreta 

 expelled with a rapidity which precludes its presence 

 within the alimentary canal for any length of time. 



THE VASCULAR SYSTEM. 



According to the histological structure of the walls, the 

 vascular spaces in Lineus are spoken of partly as lacunae 

 and partly as vessels. The lacuna? are found in the head 

 and in the oesophageal region. They are surrounded by 

 connective tissue, and their only wall consists of a delicate 

 membrane on which occur small oval nuclei at intervals. 

 The vessels, which occur only in the intestinal region, 

 possess a rather more elaborate structure. They are lined 

 by an endothelium (PL IV., fig. 2), closely packed with 

 spherical nuclei, and in which cell outlines are not readily 

 to be distinguished. This endothelium rests upon a well- 

 marked structureless basement membrane, but no circular 

 muscle fibres are present. External to the basement mem- 

 brane is a layer of large parenchyma cells, highly 

 vacuolated and with definite cell outlines. 



