188 JURA. NATURAL HISTORY. 



observed within the limits of the British seas. It belongs 

 apparently to the genus Salpa, and the accompanying 

 drawing would be sufficient to distinguish it even without 

 a specific definition.* 



The mode in which t^e republic is linked together, is 

 observed to be constant in each species ; and it is suffi- 

 ciently remarkable in this one to distinguish it from the 

 rest of the genus as far as it is yet described. Each 

 individual adheres to the preceding by a regular sequence 

 of superposition lengthwise, so that the whole forms a 

 long simple chain; the adhesion continuing, as in the 

 ovarium, for some time after hatching. They were found 

 from the middle to the latter end of August, and always 

 linked together. It is probable that their separation takes 

 place at a later season of the year, but I did not observe 

 them in that state. The individual is among the most 

 simple in shape of those yet described; presenting an 

 oval-lanceolate and slightly rhomboidal flattened figure, 

 without appendages. The anal opening is of a bright 

 brown colour and circular, being placed at some distance 

 from the extremity ; and when the chain is linked together, 

 all these apertures are directed the same way. The animal 

 is perfectly hyaline and tender ; and the adhesion of the 

 chain so slight that the individuals are easily separated. 

 The act of swimming is known to result from the intro- 

 duction and emission of water by each animal ; and as 

 the republic swims together by an undulating motion 

 resembling that of a serpent, the chain often extending 

 to many feet in length, it is evident that this motion must 

 arise from the unequal manner in which the different 

 individuals act throughout the whole line. 



The species now described is most analogous to the 

 S. polycratica and to the S. confederata of Forskahl. It 

 differs however from the former in the want of the caudal 

 denticle, in its hyaline appearance, and in the absence 



* Plate XXIX. fig. 2. 



