ASCIDIIDiE. 589 



separation, so as to expose the mantle along a ventral 

 mesial line, whilst the orifices protruded at one extremity, 

 it would present the closest similarity with many hivalve 

 Molluscs." The gills in these animals have generally the 

 form of ridges more or less complicated and seldom sym- 

 metrical, and their digestive, reproductive, and circulatory 

 organs are tolerably complicated, and disposed at the base 

 of their sac-like bodies. 



Fam. ASCIDIIDjE. 



Body sacciform, gelatinous or coriaceous, fixed at one 

 extremity, free at the other, with two more or less promi- 

 nent orifices, abranchial and an anal; branchial sac simple 

 or plicate. Not united into groups by a common integu- 

 ment ; solitary or gregarious. Oviparous. Sexes united. 



In the genera Ascidium and Molgula the gills are not 

 plicated, which is the case in the other genera. Cynthia 

 and Chelyosoma are sessile, while Boltenia and Cystingia 

 are pedunculated. On the coasts of the Channel and the 

 Mediterranean, and in the China seas some of the species 

 of these isolated Tunicaries are valued as articles of food. 

 "At Cette," says Van Beneden, " Ascidia are taken re- 

 gularly to market, and Cynthia microcosmus, although so 

 repulsive externally, furnishes a very delicate morsel, much 

 sought after bv some." 



Genus ASCIDIUM, Baster. 



Body sessile, covered with a coriaceous or gelatinous 

 tunic ; branchial orifice eight-lobed, furnished inside with a 

 vol. it. i G 



