86 ANATOMY OF THE ENOPLA. 



are situated laterally and posteriorly, forming somewhat elongated pyriform organs, which adapt 

 themselves to the curves of the ganglia (Plate XV, fig. 2). Each sac is filled with rounded 

 granular cells, reddish pigment- and other granules, has a ciliated duct opening anteriorly at the 

 constriction or lateral dimple of the head just in front of the ganglia, and posteriorly ends in a 

 ciliated tube which by-and-by bifurcates, each of the trunks giving off various branches. The latter 

 are furnished with numerous granular cells, apparently imbedded in the wall of the tubes, 

 so that in contraction they have a cellulo-granular appearance, somewhat similar to the " segmental " 

 tubes of the Oligochaeta. There are also in this species a number of branched vessels of small 

 calibre behind the ganglia, apparently in connection with the circulatory system. In the snout of 

 the same worm is a series of well-marked glandular organs in front of the nerve-centres, viz., a 

 tabulated mass (g) in the middle line, connected with a lateral (gi) on each side of the blood-vessel. 

 These glands agree in structure, containing granular cells, pigment- and other granules. A 

 process (duct ?) passed from the posterior end of the external lobule towards the cephalic sac. 

 Traces of similar glandular masses were seen in other species {e.g. A. lactifloreus) near the 

 middle line of the snout, behind the cephalic sacs, and elsewhere. In A. spectabilis the cephalic 

 sacs appear to be allied to those in the foregoing, and possess an ovoid outline with a process 

 posteriorly. In my softened specimen they were found behind the ganglia, and were filled with 

 granular cells and granules. The cephalic furrows in this species have a series of accessory 

 grooves (Plate III, fig. 7) much more developed than those in A. pulcher. In Tetrastemma the 

 sacs coincide in structure with those of A. lactifloreus, and in translucent specimens, such as 

 T.flavida, the ciliated posterior ducts are easily traced. Those of T. Robertiance resemble the 

 same organs in T. Candida. 



The slight furrows just described on the head in this group have been noticed by few 

 investigators, and only Professor Keferstein and M. Claparecle mention the occurrence of the 

 sacs ; the former using the term Seitenorgane for their signification, but his notice is very brief. 

 He figures and describes his B. splendida {A. spectabilis) as furnished with sacs at the side of 

 the ganglia, but without the ciliated ducts posteriorly; while in B. m.andilla the latter reach no 

 further back than the ganglia. M. Claparede, again, shows on each side of the eyes in the young 

 of Prosorhochnus Claparedii a blind sac, apparently unconnected with the ciliated pits above- 

 mentioned ; moreover, in the drawing of the adult animal (fig. 10) there is on each side a ciliated 

 duct, but no sac. M. de Quatrefages only noticed traces of these structures in the Enopla; for 

 he describes bridles or bands stretching outwards to the " fossettes cephaliques." In his Folia 

 bembioc he represents a large nerve passing from the anterior part of each lateral column, 

 not far behind the ganglion, and which, after a course directed obliquely forward, ends in a 

 dilated granular condition at the cephalic fossa. A similar arrangement occurred in P. humilis ; 

 but in this instance the nerve arose from the superior lobe of the ganglion, passed obliquely 

 forward and outwards, and ended in several branches at the fossa, In Cerebratulus crassus and 

 Nemertes peronea, again, he figures the nerve springing from the posterior part of the superior 

 lobe. He does not seem surprised that the nerve-trunks to these fossae should come from sites 

 so diverse as the front of the superior lobe and the lateral trunk. The disposition of 

 an important nerve in species of the same genus, or even in allied genera, is seldom 

 so varied. The structure seems to have been misinterpreted in the Enopla, the sac 

 overlooked, and the process or duct, which sometimes crosses to the origin of the great nerve- 

 trunk and ganglion of its side, assumed to be a nerve-branch. M. van Beneden, though he 



