332 
ZOOLOGY OF THE FAR EAST. 
into the oesophagus (Oe). The oesophagus runs upwards and backwards forming a 
loop; thsn becomes straight to suddenly recurve backwards. It is 11-12 mm. long 
and is held in place by the mesenteries, the arrangement of which is the same as in 
other species of the genus. The gizzard {G), which follows, is 4 mm. long, leads 
straight back and lies to the right of the nerve-cord ; from it the crop (C>) leads to 
the pre-intestinal constriction, which is marked off by the vascular ring ; the crop is 
a little more than 3 mm. long. 
The middle part of the alimentary canal or the gut is very long in all the species. 
From the pre-intestinal constriction to the origin of the siphon (Si) or collateral 
intestine it measures about 13 cm., from the origin of the siphon to its union with the 
intestine it measures about 9 cm., and from the latter point to the pouch-like 
caecum (Ca) about 17 cm. 
The last part of the alimentary canal, the rectum {R), measures 12 mm. 
The foregut of T. hranchiorhynchus is shown in fig. 11, and the whole of the 
alimentary canal as seen in a dissection of T. sabinum, in fig. 10. 
I have nothing to add to the remarkably accurate account of the histology of 
the alimentary canal of T. neptuni given by Jameson. 
Nervous system. — -The nervous system in this group is essentially similar to that 
of other Echiuroids. The single nerve-cord {Nc) is a conspicuous structure extending 
from near the mouth to the anus in the mid-ventral line. In living specimens of T. 
sahinum and T. hranchiorhynchus , and even in the preserved specimens of these spscies, 
it is quite easily seen through the skin. In T. dendrorhynchus in the preserved speci- 
mens only a faint streak is to be distinguished. The nerve-cord is not bound to the 
body-wall by mesenteries, but lies directly on the musculature. There are no n^rve- 
ganglia. It gives off lateral branches from the lateral margins at irregular intervals 
on both sides (these branches are not shown in fig. 10), which, after running free for 
a short distance, penetrate the body-wall, in which they run parallel to the circular 
muscles. Near the mouth anteriorly at its end the nerve-cord is thickened into a 
triangular area, from which two branches arise. These branches are continued for a 
short distance on the sides of the pharynx and then enter the proboscis, where they 
continue as the lateral nerve {N.l) of each side to meet near the tip and form a large 
ganglionic mass. These lateral nerves give a large number of branches in the probos- 
cis; some of these branches could be traced up to the ciliated cells but no direct 
connection was seen. 
In trying to homologize these structures with those of an annelid like the earth- 
worm it seems that the proboscis is the very much elongated prostomium and that the 
supra-oesophageal ganglion of the earthworm has shifted here to a position far for- 
ward in the proboscis, and that the two lateral nerves are the very much elongated 
circumoesophageal connectives; whilst the triangular area from which the nerves 
arise is the suboesophageal ganglion. 
Regarding descriptions of the histological structure of the nerve-cord I have 
nothing to add to the descriptions of Spengel, Reitsch and Embleton in other Echiuroids. 
Blood-vascular system. — There is a closed circulatory system as in the Echiuroidea 
