244 REPORT — 1851. 



short oesophagus, these sharp instruments are packed and folded upon them- 

 selves. M. Quatrefages, ignorant of the protrusibility of these parts, wrongly- 

 conceived that this was the permanent and immoveable position of these parts, 

 and described the chambers in which the jaws were lodged as "poches a 

 stylets." The appearance of cavities or pouches is, however, altogether delu- 

 sive, and depends upon the closing round the jaws of the sides of the pro- 

 boscis. This organ in Lineus longissunus (Sowerby) is positively several 

 feet in length, and constitutes a formidable instrument of offence*. 



It is remarkable that the very existence of this proboscis has escaped the 

 observation of ihe many excellent observers by whom from time to time and 

 under different names it has been accurately described. This organ is pro- 

 vided with a thick stratum of papillose glands (PI. XI. fig. 64 d), by which 

 doubtless a secretion is furnished important to the digestive process. This 

 glandular salivary product is poured into the channel of the proboscis : thence 

 it finds its way, mingling with the fluid food, into the oesophagus (e), wherein 

 it sojourns for a short period, and thence tra7isudes, by exosmose, through the 

 purietes and reaches the cavity of the great alimentary organ (/), where it 

 assumes by slow assimilation a higher organic standard, becoming probably 

 fitted to nourish the solids of the body, and to replenish the contents of the 

 true blood-vessels. It will be seen that there is no direct open communication 

 between the oesophageal tube (e) and the great alimentary caecum (/,/}, nor 

 between the cavity of the latter and the exterior. The contents of this great 

 cavity must, therefore, in great part at least, be recrementitious, not excre- 

 mentitious. 



The oesophageal intestine terminates (fig. 64 g^ in a distinct papillose outlet, 

 which is situated at a short distance posterior to the cephalic end ; when the 

 proboscis is withdrawn into the interior of the body, the oesophagus lies in 

 the cavity of the great alimentary ceecum, being traceable back to some di- 

 stance in the direction of the tail. While in this position, this tube may be 

 readily, as it always has been, mistaken for a true intestine ; followed more 

 minutely, however, it may readily be observed to return upon itself and ter- 

 minate in the lateral outlet already indicated. In the mere mechanical dis- 

 position of these parts an intimate analogy may be remarked between the 

 Nemertinidce and the Sipunculidce, in which the alimentary canal coils upon 

 itself and ends in an outlet situated ventrally, about the anterior third of the 

 body. In this case, however, there is no other alimentary organ, in which 

 respect the Sipunculidce differ most fundamentally from the Nemertinidce. 



The great spongy mass which in the geneca Borlasia, Lineus and Gor- 

 dius, constitutes so considerable a portion of the whole bulk of the body, com- 

 mences anteriorly, immediately behind the hearts (fig. 64 a, a), under the cha- 

 racter of a ccecal end (h). Although the oesophagus enters {appears to per- 

 forate) into the contained cavity of this organ at this situation, yet the interior 

 of the latter is not laid open, for its parietes are reflected over and embrace 

 those of the oesophagus. Nor is it possible to discover at any part of the 

 course of this tube any direct opening of any sort leading from it into the 

 cavity of the digestive ccecum. It is, notwithstanding, from the relative con- 

 nexion of these parts, impossible to doubt that the food passes from the 

 oesophagus, after a short detention therein, for the purpose of insalivation, 

 into the interior of the digestive caecum. In the absence of all proofs of a 

 direct opening between these two cavities, the passage of the food can only 

 be accomplished by transudation through the parietes of the oesophagus. 



* Several specimens of this extraordinary ■worm have recently been found on the shores 

 of the Bristol Channel, one by Mr. Lewis Dillwyn, one by Mr. Moggridge, and several by 

 myself. 



