316 
THE OCEAN WOULD. 
The genus Salpa forms another interesting group of Tnnicata. 
The Biphoraor Salpa (Fig. 126) are long transparent threads of the 
most delicate tissues, composed of rows of individuals placed side by 
side, and grafted, as it were, transversely : ribbons, in which each 
animal is grafted end on end to its sister : double parallel chains ol 
social creatures, sometimes alternate, sometimes opposite : living chap' 
lets, of which each pearl is an individual. Each individual presents 
an oblong diaphanous or prismatic body, more or less symmetrical! 
and often furnished in front, rarely behind, with tentaculiform ap' 
pendages. So great is the transparency, that the various organs may 
be observed through the skin as they perform their several functions. 
An ancient philosopher thought it a subject of regret that Nature 
had not thought of piercing the body with an opening sufficiently 
Fig. 126. Salpa maxima (Forsk). 
large for each one to see what was passing in the interior. Th° 
creature which now occupies our attention would surely have satisfied 
the demands of our critic : its body is, metaphorically speaking, a 
house of glass. 
In order to move itself, the Salpa has recourse to a singular artifice- 
It introduces water into its body through a posterior opening, furnished 
with a valve, which it expels by an anterior outlet situated near tb e 
mouth. It is thus pushed backwards, and swims, as it were, by recoil- 
Moreover, it swims with its belly upwards. All the elements of a 
chain of Salpas act in concert ; they contract and dilate simultaneously > 
they advance as a single individual. One of them floats on the surfac 0 
with the undulations of a serpent, so that, among sailors, they hav 0 
gained the appellation of sea-serpents. These long, living tram 
abound in the Mediterranean, principally towards the African coast, 
