CIONA INTESTINALIS. 13 



is wider than the oesophagus and is of equal calibre 

 throughout; and in passing from the dorsal to the 

 ventral margin it forms a deep sigmoidal curve, or 

 two open loops, and then, turning upwards it advances, 

 adherent to the ventral margin of the branchial sac for 

 some distance, to the atrium, where it opens through 

 a wide orifice with a reflected, denticulated margin. 

 The ovary lies suspended in a membrane Avithin the 



FIG. 28. Mantle of dona intestinalis. Natural size. v.t. Blood-vessel 



leading to test. 



first intestinal loop and at the right side of the 

 stomach ; it is an elongated clavate body with the 

 thickened extremity curved ; and the attenuated end 

 turned towards the ventral margin. The oviduct is 

 given off from this tapering extremity, and, accom- 

 panied by the vas deferens, it advances upwards by 

 the left side of the intestine, opening into the upper 

 portion of the atrium considerably in advance of the 

 anal orifice ; the extremity is enlarged into a small 

 bulb. The male cgeca are quite minute and are 



