and Anatomy of the Thalassema and Echiurus. 373 



■which is sacculated and contracted at intervals, particularly 

 in its posterior half. This first portion of the intestinal ap- 

 paratus, which may be denominated the pharynx, is arranged 

 in two coils so as to resemble somewhat the figure 8. These 

 coils are compressed and kept in position by the muscles of 

 the oral hooks, and by the bloodvessels, which assume a com- 

 plicated arrangement in this part of the animal. The tube 

 then contracts into a highly muscular but very narrow oeso- 

 phagus. This rather suddenly dilates into the remaining part 

 of the canal, which is nearly uniform in diameter, thin and 

 delicate in texture ; arranged in a somewhat spiral direction 

 till near the posterior part of the animal, returning upon itself 

 in the same manner for two-thirds of the length of the body, 

 and then proceeding to the cloaca as a straight and rather 

 narrow tube. The cloaca is smaller than the same organ in 

 the Holothuriadw. From mouth to anus the canal measures 

 from three to four feet. The pharynx is two inches long, the 

 oesophagus four, and the remainder is so uniform in diameter 

 as to render it impossible to distinguish any division into sto- 

 mach, intestines, &c, and so fragile as to render measurement 

 very difficult. The pharynx exhibits distinct circular muscu- 

 lar fibres, and in the oesophagus they are so strong and so ar- 

 ranged in bundles as to give it the appearance of a windpipe. 

 The tube is not connected to the parietes of the body by a 

 mesentery, but by numerous delicate muscular threads irre- 

 gularly arranged and intermingled with minute bloodvessels. 

 Near the middle of the body the folds of intestines are filled 

 with a yellow bilious mass, but we could detect no trace of a 

 liver, or of glandular structure in the coats of the gut. 



The respiratory sacs open into the cloaca on each side of the 

 rectum. These sacs do not ramify, and are about one-third of 

 the length of the animal, and exhibit in the living individual 

 lively motions — contracting, dilating, elongating and twisting. 

 They are of a vivid red colour from the number of vessels dis- 

 tributed to them, and have a mottled appearance from nume- 

 rous microscopic organs attached to their external surface. 

 When a small portion of the respiratory organ is cut from the 

 living animal and placed under the microscope in a little sea- 

 water, the dots observed with the nuked eye on its outer or 



