NEMERTEAN HELMINTHOZOA. 



155 



Fig. 77. 



like that of the Planaria described above, is a most efficient instrument 

 for seizing prey. Immediately behind the proboscis is situated a very 

 remarkable apparatus in the shape of an extremely muscular oesophagus, 

 wherein is lodged a weapon of most extraordinary character, consisting 

 of a solid transparent spiculum, lodged in a cavity, formed in the thick- 

 ness of the oesophageal parietes, wherein is contained a glandular mass, 

 by which the calcareous spiculum is apparently secreted (fig. 77, #). 

 Other glandular structures (h h), probably destined for the elimination 

 of some venomous secretion, are in communication with the styliferous 

 cavity ; so that the dagger-like spiculum, being constantly bathed with 

 the secretion thus furnished, becomes an instrument of a very deadly 

 character. The dagger-like weapon, together 

 with its immediate appendages, is capable of 

 being protruded by the aid of muscular bands 

 in connexion with the styliferous cavity, which 

 at the same time, by compressing the glands, 

 readily cause the emission of their secretion. 

 On each side of the formidable apparatus above 

 described, there are, moreover, two other cavi- 

 ties, apparently of an auxiliary character (fig. 

 77, i i), in which a secretion of supernumerary 

 spicula is perpetually in progress, apparently 

 destined to replace the original one if lost or 

 broken. 



(412.) The intestine (fig. 77, 6), properly so 

 called, succeeds immediately to this strangely 

 organized oesophagus, and is continued back- 

 wards, floating in the central compartment of 

 the body,- to which it is loosely attached by 

 membranous bridles for about three-fourths of 

 the length of the worm, at which point its 

 calibre rapidly diminishes and its cavity soon 

 becomes obliterated, so that it terminates 

 under the aspect of a simple cord. 



(413.) The Nemertean Helminthozoa are 

 possessed of a very complete circulatory system 

 of vessels enclosed in proper walls. These 

 consist of three principal trunks, two of which 

 run along the sides of the ventral aspect of the 

 body (fig. 76, i i), while the third occupies the 

 middle of the dorsal surface (fig. 76, 1 1} : these 

 three vessels become considerably increased in size as they approach the 

 posterior extremity of the worm, and ultimately are conjoined. 



(414.) The median vascular trunk, throughout the greater part of its 

 course, is situate immediately beneath the subcutaneous muscular layers ; 



Styliferous apparatus of Folia 

 mandilla: a, portion of pro- 

 boscis ; 6, portion of the intes- 

 tine ; c, first oasophageal dilata- 

 tion; d, second cesophageal di- 

 latation ; e e, cesophageal canal, 

 presenting sundry dilatations 

 and contractions ; f, cavity in 

 which is lodged the spiculum, g ; 

 h h, poison ?-glands in connexion 

 with the spiculum, g; i i, cavities 

 enclosing incompletely formed 

 spicula. 



