200 THE DIGESTIVE SYSTEM. 



delivered, through a contracted, hut still rather wide 

 gullet, into an ohlong stomach, the lower portion of 

 which is ohtuse. An extremely attenuated duct con- 

 nects this, which is prohahly the true stomach, with a 

 globular, rather small, intestine, which is again con- 

 nected by a lengthened thread with the base of the cell. 

 By an arrangement common 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 upwards parallel to 

 the gullet, and terminates by an orifice outside and 

 beliind the base of the tentacles. All these viscera 

 are beautifully 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 colour. All of them are manifestly granular 

 in texture, except the slender 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 polype into its cell 

 upon disturbance or alarm, and its slow and gradual 

 emergence again, afford excellent opportunities for 

 studying the forms, proportions, and relative positions, 

 of the internal organs. In contraction, the globular 

 intestine remains nearly where it was, but the stomach 

 slides down into the cell behind it, as far as the flex- 

 ible duct will allow, and the thick gullet bows out in 

 front, shewing more clearly the separation between it 



