BRANCHIAE OF TUNICATA. 



281 



branchial surface of the Asciclia pedunculata (Boltenia ovi- 

 fera, Sav.), highly magnified, and is an example of its usual 



Fig. 50. 



J r 



if — -m 



Pattern of the branchise in 

 Ascidia peilunculaia. 





hull line'' 



Pattern ot the Lianchiaj in Ascidia 

 mytiligera. 



and least ornamental conformation ; in the Ascidia (Cynthia, 

 Sav.) mytiligera the meshes are elliptical (Fig. 50) ; and 

 they have the same form in many other species, more par- 

 ticularly in the compound families, or those in which a 

 great number of individuals are united together in a com- 

 mon system. (Fig. 51). Again, in some genera, of which 



Fig. 51. 



Fis. 52. 



Pattern of the branchiae in Phallusia 

 sulcata. 



the Phallusia of Savigny is one, 

 there is a small conical process at 

 each angle of every little square 

 (Fig. 52) ; but it is in the Cyn- 

 thia Dione that the most remark- 

 able modification of this struc- 

 ture appears. Here the branchial 

 tissue is not continuous upon the 

 folds of the sac, but interrupted, 

 at equal distances, in a manner 

 to resemble a series of very regular festoons. Each fold 

 has a second at its base, which is not free like itself, and 

 of which the points of fixture correspond to the intervals 



Pattern of the branchia; in Pylo- 

 clinuin hesperium. 



