SEA-MATS AND SHELLY CORALLINES 83 



mon to the ascidian type of the digestive function, the food 

 is returned from the intestine into the true stomach, whence 

 the effete parts are discharged through a wide and thick 

 tube that issues from it close behind the point where the 

 gullet enters. This rectal tube passes upward parallel to 

 the gullet, and terminates by an orifice outside and be- 

 hind the base of the tentacles. All these viscera are beau- 

 tifully distinct and easily identified, owing to the perfect 

 transparency of the walls of the cell, the simplicity of the 

 parts, and their density and dark yellow color. All of 

 them are manifestly granular in texture, except the slen- 

 der corrugated tube which connects the stomach with the 

 globose intestine: this is thin and membranous, and is 

 doubtless, if I may judge from analogy, capable of wide 

 expansion for the passage of the food-pellet. 



The sudden contraction of the polypide into its cell 

 upon disturbance or alarm, and its slow and gradual emer- 

 gence again, afford excellent opportunities for studying 

 the forms, proportions, and relative positions of the in- 

 ternal organs. In contraction, the globular intestine re- 

 mains nearly where it was, but the stomach slides down 

 into the cell behind it, as far as the flexible duct will 

 allow, and the thick gullet bows out in front, showing 

 more clearly the separation between it and the rectum, 

 and the insertion of both into the stomach. This retrac- 

 tion is, in part, effected by a pair of longitudinal muscu- 

 lar bands, which are inserted at the back of the bottom 

 part of the cell, and into the skin of the neck below the 

 tentacles. The contraction of these bands draws in the 

 integument, like the drawing of a stocking within itself, 

 and forces down the viscera into the cavity of the cell, 

 which is probably filled with the vital juices. 



