38 ALTERNATE GENERATION 



CHAPTER III. 



THE ALTERNATE GENERATION OE THE SALPiE. 

 (Pkoles Gkegata, Proles Solitakia.) 



In the preceding chapter it must certainly have 

 occurred to every one, that phenomena w^ould also be 

 presented among the Mollusca, particularly in the Salp^e, 

 analogous to those exhibited in the development of the 

 Medusce and Corynm. These animals have attracted the 

 notice of all voyagers, by the extraordinary circumstance, 

 that numbers of individuals, 20, 40 or more, are united 

 into very long chains {ßalpa chains) in a peculiar manner 

 and by means of special organs of attachment. All 

 the individual Salpce composing these chains, are of the 

 same form, and are opposed to each other in the same 

 direction; they move with great uniformity, and keep 

 as it v^^ere the same time, by v^^hich movement the vv^hole 

 chain progresses in a serpentine manner, belov^^ the 

 smooth and tranquil surface of the water ; for, like other 

 gelatinous and transparent marine animals, they approach 

 the surface of the sea, only in fair and calm weather. 

 Besides the Baljp(ß which are thus united in chains, there 

 are also other individuals which are not so joined, but 

 swim about separately. Some of these exhibit evident 

 traces of theu having previously been united, since they 

 possess the organs by which they had been attached, 

 and their shape exactly resembles that of the associated 

 animals; but in others, all trace of their having been 



