244 



Natural History of Molluscous Animals : 



you have here copied from the beautiful plates of Savigny. 

 Fig. 3 I. exhibits a small portion of the branchial surface of 

 the Ascidia pedunculata (Boltenm ovifera Sav.), highly mag- 

 nified, and is an example of its usual and least ornamental 

 conformation ; in the Ascidia (Cynthia Sav.) 7wytiligera the 

 meshes are elliptical (Jig. 32.); and they have the same form 

 in many other species, more particularly in the compound 

 families, or those in which a great number of individuals are 

 united together in a common system. (Jig. 33.) Again, in 



-ilq; 



M* 34 





Pattern of the branchiae in Phall&sia 

 sulcata. 



some genera, of which the Phallusia 

 of Savigny is one, there is a small 

 conical process at each angle of 

 every little square (Jig. 34.); but it 

 is in the Cynthia Dione that the 

 most remarkable modification of this 

 structure appears. Here the bran- 



PatternofthebranchiasinPolycllnum chial tissue is not COntinUOUS UDOn 

 nesp&num. . _ 1 . _ . . . r , 



the tolas ot 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 which separate the festoons. 

 The whole of the plaits are twenty-eight, fourteen on each 

 side, and they are margined by an equal number of great 

 longitudinal vessels. The vessels which compose the tissue 

 are excessively fine ; the transverse, however, less delicate 

 than the others, and not so closely set, accommodate them- 

 selves very well by their curvature to the outline of the fes- 

 toons. This description, I feel, needs the aid of Savigny's 

 figure, of which I gladly avail myself, and I am certain that 

 in few other creatures will you find a structure more wonder- 

 fully fashioned. (Jig. 35.) (Mem. sur les Animaux sans Ver- 

 tebreS) 2de partie, passim). 



Although the branchial tissue apparently covers the whole 

 inner surface of the sac with a continuous network, yet it is 

 bns iB3i^t Jjuil 9 ' 



