212 THE DIGESTIVE SYSTEM. 



disk, the edges of which then close together and form 

 a puckered nipple, and the whole head becomes pear- 

 shaped, in which state the animal might be mistaken 

 for some large species of the stationary Rotifera. 



The colour of the wdiole animal is pellucid white, 

 and viewed by reflected light, gives us no insight into 

 its internal structure. It is only when examined as a 

 transparent object that its interior is at all revealed. 

 Even then the intguments are but imperfectly trans- 

 parent; the whole animal, body, stalk, and stem, is 

 covered with a thick coat of gelatinous matter, which 

 is viscous, and in which Diatomacece, and other ex- 

 traneous bodies, become entangled ; the whole exter- 

 nal surface is either granular or slightly corrugated, 

 and transmits the rays of light tinged with yellowish 

 brown ; these circumstances, combined with the over- 

 lying of the viscera in the globose body, render the 

 internal parts difficult of determination. It appears, 

 however, that the funnel of the disk proceeds diagon- 

 ally downwards, until it nearly reaches the wall of the 

 abdominal cavity on the ventral side. It then sud- 

 denly turns, and (as I think) performs several convo- 

 lutions transversely across the body. At length it 

 merges into a capacious sac which occupies the whole 

 of the lower part of the cavity of the body. It appears, 

 however, as if the centre only of this sac were void, 

 for granules of the food may be observed, in almost 

 every individual, agglomerated into a somewhat loose 

 lengthened pellet, which continually revolves on its 

 long axis. This food-pellet becomes visible as a 

 slender thread near the middle of the sac, and passes 

 diagonally upward, increasing in size as it advances 



