416 SUPPLEMENT 
There are very great singularities in the product of genera- 
tion, or the offspring of the salpez. It may be solitary, or 
united with a great number of individuals similar to itself, the 
union of which takes place in a constant manner by means of 
those organs to which the name of suckers, or spiracula, has 
been given. 
The single or solitary foetuses appear considerably to differ 
from the individual from which they come; so much so, 
that according to Messrs. Quoy and Gaimard, without being 
apprized of the fact, one might be disposed to set them down 
as distinct species. They are suspended in the cavity of the 
mantle by a sort of cord, which M. Chamisso names the um- 
bilical cord. MM. Quoy and Gaimard also speak of a pedicle 
attached to a sort of placenta, filled with mucous matter. 
M. Chamisso informs us that the species of this genus pre- 
sent themselves under a double form, a race entirely dissimilar 
to the mother, during the whole course of its life, nevertheless. 
producing young ones all similar to her, so that a salpa 
which differs equally from its parent, and its own children, 
resembles its grand-parent, its grand-children, and its own 
brethren. In both states, the salpa is androgynous, or to 
speak more correctly, female, and equally viviparous ; but in 
one the product of generation is a solitary animal, and mul- 
tiparous ; in the other, it is a stérps composed of individuals 
united together in a determined manner, and oviparous. 
Thus each species presents a solitary, and an aggregated 
race, equally capable of reproduction. 
Many animals of this genus produce eggs enchained toge- 
ther, and from each egg comes an animal entirely similar to 
its parents. But the solitary race, instead of eggs, produce 
animals thus enchained, from each of which, as from an egg, 
issues a solitary salpa, similar to the first mother; so that 
we might say, that the solitary race is an animal, and the 
enchained race is nothing but a mass of aggregated and living 
