OF TREPANGS. 189 



across, and the posterior end gradually tapers from a short 

 distance behind the thickest mid-region of the body. As they 

 lie on the beach after being cast up by a storm, the Caudinas, from 

 their shape and fleshy color, might easily be mistaken, at a dis- 

 tance, for so many human fingers lying loose and idle. The 

 mouth is a simple aperture in the middle of the truncate head. 

 The latter is bordered right and left by a row of cross-tipped, 

 hollow, cylindrical feelers, (/, 2 1 ,) so disposed that one of them is 

 in the lower middle line of the body, directly under the mouth, 

 and a pair in the upper median line, and the remaining twelve 

 lie, six on each side, at equal distances apart, between these two 

 points. 



From the mouth, the passage into the stomach is through a 

 simple, broad, tubular throat, (,) which expands slightly as it 

 joins the latter. The stomach and intestine are so uniformly 

 tubular that it is not possible to make a proper distinction 

 between them, and I shall therefore designate the whole di- 

 gestive canal as the intestine. This organ extends at first back- 

 wards, a little to the left of the median line, through two thirds 

 the length of the body, and then abruptly making a fold, (g- 1 ,) it 

 advances along the right of the median line, as far as the an- 

 terior third of the body, and then again redoubling itself, (g- 2 ,) it 

 passes backwards with a gradual taper (g 8 ) to its posterior 

 termination (g 4 ) at the end of the tail. Throughout its whole 

 tract there is but one pair of hollow appendages, (figs. 114, 115, 

 rt, rt 1 , r 2 ,) and these arise from that part of it which lies just 

 behind its first fold, one from the left and the other from the 

 right of its upper side. At their point of attachment (rt) they 

 open widely into the intestine, in the same way as do the ten 

 puckered appendages of the starfish (fig. Ill, st l ). The main 

 tube (figs. 114, 115, rt 1 ) of these appendages gives off in every 

 direction numerous processes which branch like the twigs of a 

 tree, and extend themselves throughout the whole circum-intes- 

 tinal cavity, even to the extreme anterior end of the body (fig. 

 114, rt 2 ). On account of their peculiar conformation, and their 

 supposed office as respiratory organs, they have been called the 



