A Simple Tunicate. 137 



If the specimen is viewed from the dorsal side, a circular 

 line will be found to extend from the anterior end of the 

 endostyle around either side of the oral siphon to the 

 ganglion. This line marks the position of the peripharyn- 

 geal bands. 



Drawings of the right and left side of the animal should 

 now be made. 



By gently pressing upon the mantle it will be shown that 

 there is a space between it and the deeper lying branchial 

 bands. This space is the atrium or peribranchial chamber, 

 and can be beautifully seen if one now carefully removes the 

 cloacal siphon by cutting around its base, beginning just 

 above the ganglion. The cavity thus opened is actually the 

 cloacal chamber, though the right and left halves of the peri- 

 branchial chambers are seen to lead directly from it as we 

 look down through the artificial opening. The branchial 

 folds are now seen to form the longitudinal ribs of a reticu- 

 lated sac, the branchial sac or pharynx. Crossing the bands 

 at right angles are certain transverse vessels, and stretched 

 between vessels and ribs is a delicate membrane pierced by 

 minute openings or stigmata. 



On the branchial sac a dorso-median line will be observed 

 to extend from near the ganglion to near the posterior end 

 of the endostyle. The anal opening will be found near the 

 lower end of this line. The intestine lies along the floor of 

 the left peribranchial chamber, and is often deeply colored 

 from the presence of contained faecal matter. The openings 

 of the genital ducts are to be seen on the right and left 

 external branchial walls respectively. The cloacal chamber 

 receives then the waste products of digestion, the secretion 

 of the sexual glands, and also the water which flows into it 

 directly through the stigmata of the posterior wall of the 



