234 REPORT — 1851. 



ternal surface of this part of the tube, in form of transparent vesicular tubuli 

 filled with minute cells. To the oesophagus in all SyllidcB succeeds an elon- 

 gated highly glandulated gizzard-like portion peculiar to and characteristic of 

 this genus (fig. 59 d). The parietes of this portion are not perhaps dense and 

 muscular enough to claim for it the character of a true gizzard. The glan- 

 dules are arranged in transverse or circular rows, and communicate with the 

 interior by means of a minute excretory tube or orifice. One type of struc- 

 ture prevails throughout all varieties of the secernent glandules, whether 

 biliary or salivary, discoverable in the digestive system of the Annelida. They 

 resolve themselves, in ultimate analysis, into membranous capsules filled with 

 secondary cells, for the most part oleous. These cells are contained in a 

 plasma, out of which they draw the material of their own formation and in- 

 crease. They dehisce and contribute thus a perfected secretion, adapted to 

 perform a part in the chemical and vital processes of digestion. The biliary 

 intestine in these worms presents a deeply notched outline, approaching the 

 moniliform (fig. 59 e). The segments of that part which immediately succeeds 

 to the gizzards are very much elongated, while those nearer the tail present 

 annulations corresponding with those of the integument. The biliary layer in 

 these worms is not pigmented.bright yellow, but dull yellow, having a greenish 

 tint. There is nothing demanding notice in the formation of the rectal 

 intestine in the Syllidce. The outlet is situated dorsally and above a small 

 median style. As the blood-proper is destitute of colour, there is little diflS- 

 culty in explaining the absence of brilliant pigments from the solid glandular 

 structures of the body. 



The genus Sjno or Nerine comprehends two well-known species, N. vul- 

 garis and N. coniocephala ; to which number the author has lately added 

 N. Marcella. These Annelids are notorious for the extraordinary accumu- 

 lation of faecal matter which occurs in the posterior half of the intestinal 

 canal, causing the whole of this moiety of the body to look closely like an 

 inanimate string of sand and earthy substance. This character is more 

 striking in the two last-named species than in the first. Spio vulgaris is an 

 active ivorm, and the posterior half of the body does not drag like a lifeless 

 appendage, as it does in *S'. coniocephala and S. Marcella, These worms 

 are improboscidean. The head terminates in a prolonged tapering snout. 

 The mouth is situated ventrally and a little behind the extreme end of the 

 head; the lining membrane of the pharynx is capable of being only very slightly 

 exserted. It is by the operation of the arms that food is conveyed to the 

 mouth. The chief part of this food consists of sand, fragments of shells, &c. 

 In consequence of the conical figure of the snout, these worms penetrate the 

 gravelly and shelly soil in which they are found with great facility. That 

 portion of the body which corresponds with the oesophagus, contrasts prettily 

 by its dull white colour with the rest of the body, which is dark green. The 

 oral two-thirds of the oesophagus is a smooth tube, unsupplied with glands 

 (Plate X. fig. 60 a) ; the remaining portion, as far as the intestine, embraced 

 by a flocculent layer consisting of a vast multitude of follicular glandules (b). 

 They coincide in structure with those which in the carnivorous Annelids 

 beset the proboscis. The first fifth of the true intestine is generally empty 

 and thickly furnished with parietal biliary glands. At this part the colour 

 is dark green. The perfect yellow does not appear in these worms. Next 

 to this portion occurs the colonic segment of the canal, which is distin- 

 guished by its earthy contents, the dark green of the integuments becoming 

 sensibly diminished, enabling the contents of the canal to contrast strongly 

 with the anterior portions of the body. The segmentations of the anterior 

 part of the intestinal canal are deeply marked, the tube being reduced at 



