ON THE BRITISH AMNELIDA. 339 



the constricted intervals to a fine thread, through which, into the contiguous 

 segment, a minute portion of faecal matter periodically passes. The biliary 

 glandules on the parietes of the intestine present a definitively linear arrange- 

 ment ; that is, when traced around the cylinder they form circular rows of 

 glands. 



In (r/ycera a/ia (Plate XI. fig. 61), the alimentary canal is remarkably 

 moveable ; it is tied to the integumentary by bridles of muscular fibrillae. 

 This most attractive and lively little worm inhabits loose moist sand, tlirough 

 which it progresses by frequent thrusts forwards with its proboscis. The jaws 

 of this organ are four in number, hook-shaped (fig. 61 a), each presenting a 

 secondary piece projecting from the back; the base being strong and 

 broad. The extremity of the proboscis is smooth, while the posterior four- 

 fifths is thickly villose with papillary glandules (fig. 61 i). The oesophagus 

 exceeds the proboscis in length, enabling the latter to be packed upon the 

 former. The intestinal segmentations commence at the oesophagus ; there is 

 no proper stomach. The functions of the stomach are merged either in 

 those of the proboscis, or in those of the biliary intestine. In numerous ex- 

 amples it has already been shown that this conformation is frequent among 

 the Annelids. From the peculiar character of those ' zones ' of the sea-shore 

 in which this worm is ordinarily found, it is probable that it subsists on the 

 organic material contained in the soil, of which it swallows considerable 

 quantities. 



Nephthys Hombergii is commonly discovered in fine sand, saturated with 

 sea-water. It swims with facility. Its proboscis presents a formidable ap- 

 pearance. It is edentulous, the jaws being, however, replaced by fine but 

 strong fleshy bristly processes. The digestive canal is found in general 

 heavily laden with the sandy refuse of digestion. Its parietes are pigmented 

 with a bright yellow colour ; the oesophagus slightly exceeds in length the 

 extended proboscis ; the intestinal canal is annulated in correspondence with 

 the integumentary. The constrictions between the segments are only slightly 

 marked. 



I4 may with great probability be affirmed generally of those worms which 

 subsist by swallowing the soil in which they live, that the real food is a 

 mixture of animal and vegetable matter, since the soil of the sea-shore 

 abounds as much in minute fragments of algaceous vegetation as in living 

 and dead animal matter. No part of the body of these worms is coloured 

 by the contents of the intestine. The whole animal presents a general dirty 

 mother-of-pearl appearance. They attain a considerable size, and exhibit in 

 the adult state extraordinary muscular power. The oesophagus in this worm 

 supports a very long single vessel — the cylindrical heart. It is little vascular, 

 and quite devoid of follicular glandules ; these latter are restricted to the 

 proboscis. The oesophagus is a strongly muscular tube, in consequence of 

 the part which it is required to perform in the protrusion and retraction 

 of the proboscis. The proboscis, being a large bulky appendage to the oeso- 

 phagus, gives to the latter, when withdrawn, an apparently greater diameter 

 than any part of the intestine. The absence of a vascular web on the parietes 

 of the oesophagus, excludes it from the physiological actions of digestion ; it 

 is in this worm, as in many others, a mere mechanical tube. The biliary 

 intestine is highly vascular; it is embraced, in conformity with the dorsi- 

 branchiate type of the intestinal circulation, by four large longitudinal 

 trunks, from which lateral vessels proceed to form a dense reticulation of 

 capillaries. It is in the minute spaces between these ultimate vessels that 

 the biliary glandules are lodged. 



In the organization of the digestive canal of the AriciadcB, there is little to 



