112 ANATOMY OF THE ANOPLA. 



nerves, and extending to the tip of the snout ; this, of course, is at variance with a true interpre- 

 tation of the structures in the Anopla. 



The cephalic fissures, as characteristic of the typical Lineidce, are absent in Carinella annulata, 

 their places being supplied by two pale curved grooves on the dorsal and two continuous 

 transverse farrows on the ventral surface of the snout. The depressions are richly ciliated. In the 

 remarkable form from Balta, the snout is surmounted by two curious frilled processes (Plate XXI, 

 fig. 9, b), which terminate posteriorly in a long filament. Whether the latter, however, is a 

 structure sui generis, or only some normal constituent of the body (such as a nerve) in a peculiar 

 position, the state of the specimen forbids our determining. 



The cephalic fissures and furrows are entirely absent in the family Cephalotkrieida. 



9. Cephalic Sacs. 



At the posterior end of each lateral fissure, a funnel-shaped tube (m? Plate XIX, fig. 1) 

 leads into a large globular structure (m), often of a pinkish or reddish hue, and the apparent 

 homologue of the cephalic sac in the Enopla. The globular body lies over the origin of the great 

 nerve-trunk on each side, and abuts so closely on the posterior prominence of the upper lobe of 

 the ganglion, as to have led some observers into the error of supposing it only a continuation of 

 the ganglionic texture. Very careful preparations and examinations of the adult animal, 

 as well as observations on the young at various stages, remove all doubt on this subject, and show 

 that these globular structures belong neither to the nervous nor the circulatory system. The 

 funnel-shaped duct (m) is richly ciliated, and the cilia may be traced to the sac, wherein they are 

 continued as a linear streak along its outer border, but its general mass is not furnished with 

 these organs. The ciliated curve along the external margin is well seen in young specimens, but 

 its exact superficial extent is difficult to determine. In favourable examples the walls are observed 

 to contain finely granular cells, which have a clear and distinct nucleus. These cells are most 

 evident on the inner and posterior curves, the outer curve being pale. The sacs project pos- 

 teriorly into two large cavities — continuations of those indicated in Plate XX, fig. 1, s, s, on each 

 side of the proboscidian tunnel, and are thus laved by the circulating fluid, which rushes forward 

 from the walls of the digestive cavity ; but there is nothing to support M. van Beneden's views 

 as to their continuity with the circulatory system. Their relations to the ganglia have been 

 adverted to already, and are well shown in some horizontal sections, where one sac has been 

 severed considerably lower than the other. 



Just in front of the external border of the curved dorsal groove on the snout of Carinella 

 annidata (Plate XVII, fig. 24) is an ovoid body apparently homologous with the foregoing, but 

 I have not yet been able to trace its anatomy, on account of the opacity of the cutaneous tissues 

 in this animal. 



The sacs are absent in Cephalothrisc. 



The function of these bodies may be excretory. Their gradual advance in position, and 

 proportional diminution in size in the developing animal, are interesting features in this respect. 

 Prof. Keferstein does not enter into structural detail with regard to these organs in this group, 

 but states that they lie at the posterior end of the lateral fissure. In Lineus sanguineus he 

 mentions they are in connection with the under surface of the ganglia, whereas they are situated 



