318 TUNICATA.—SALPADA. 
Other genera in this family form similar encrust- 
ing masses, but the animals are placed in irregular 
tortuous lines instead of stars, and the two orifices 
are near together. Others do not encrust foreign 
substances, but are grouped in variously shaped 
knots, or fruit-like bodies, adhering to stones and 
shells. 
FAMILY SALPADA. 
(Swimming Ascidians.) 
The body in this group is free, or not adherent ; 
more or less cylindrical; with a thick external 
envelope, which is somewhat cartilaginous; trans- 
parent; having the two orifices, which are ordina- 
rily very large and distant, nearly terminal, one at 
each extremity. The branchie, in the form of a 
narrow band, traverse obliquely the respiratory 
cavity of the receiving orifice to the aperture of 
the mouth. 
M. de Blainville remarks, that one may easily 
perceive the relationship of this family to the other 
Tunicata, by supposing an Ascidia slit between the 
two tubes which terminate it, and then extended 
lengthwise. It is then, he observes, easy to 
determine the analogy of the apertures, of which 
neither the one nor the other is properly any more 
the mouth or the anus than in the Ascidie ; but 
one (the widest, the greatest, and the most distant 
from the mouth), is the entrance of the incretory 
or respiratory tube, and the other is that of the 
excretory tube. He adds, that the species of 
this family are, like those of the preceding, suscep- 
tible of living solitary, or aggregated in a fixed 
