AND DEVELOPMENT OF PYROSOMA. 
197 
of which four ascend on this neck, while the others go to the opposite side. The pos- 
terior tubercle, which is here inferior, though very apparent in certain individuals, is 
imperceptible in most. There arise from it four opake yellowish or brown vessels, which 
traverse the lower side of the tunic; they are evidently the four cords of the dorsal 
groove of the Ascidians*. Along the upper edge, opposite the four cords of the dorsal 
groove, are seen two wide, short canals, of a yellow or muddy-brown colour, placed 
parallel, and so closely united that they might be regarded as a single canal, bent like 
a siphon, and extending from the middle of the branchiai to the oesophagus, where its 
two extremities end. The interior appears to be cellular f. 
tt 
This organ, which is sometimes empty and transparent, seems to me to be analo 
to that which M. Cuvier regards as the ovary of the Salpa, or at least as their oviduct ; 
perhaps it is, at the same time, oviduct and fecundating organ. 
" The ovaries % are orbicular or pyriform, symmetrically opposed to one another, and 
placed on the sides of the neck of the branchial opening, between the tunic and the bran- 
chial network, which they usually overlap. They communicate with two small, sometimes 
coloured ducts, which embrace the neck and descend as far as the loop formed by the 
siphon-like canals. These ovaries contain a multitude of rounded, very small, but very 
distinct ova. 
" If I do not deceive myself, the manner in which these germs arrive at maturity is 
very curious. It would appear that while very small they become detached, one by one, 
from the ovary, and are successively lodged between the intestine and the bottom of the 
tunic ; there they continue to grow and to be developed, until their final expulsion. 
" In fact, we almost always find in this locality an isolated germ, which varies much in 
size. While small, it is only a perfectly white and transparent globule, in which a round 
aperture, like a mouth, is discernible ; when somewhat larger, this hollow globule already 
exhibits four little reddish spots ; and when larger still, these four spots have become a 
chain of four small but distinct little foetuses, which encircle the globule for three-fourths 
of its circumference. Lastly, when it has acquired its full size, the four fcetuses, provided 
with all their organs, are united and form a complete ring. In this state it equals a 
third of the size of the individual which encloses it. It is, as one sees, a new Pyrosoma 
already composed of four animals, and will very soon be independent of the large Pyro- 
soma in which it has originated. How does it escape ? I know not. If, as is probable, 
it makes its exit by the same aperture as the excrements, this opening must be capable 
of undergoing excessive dilatation. 
" These observations, taken in conjunction with those which I have made wponBotryl- 
lus, demonstrate that the corpuscles contained in the ovaries of these animals are com- 
pound germs, not intended for the growth of systems, but for their multiplication. On 
The « anterior tubercle ' is the nervous ganglion ; the posterior, merely the anterior end of the endostyle, which is 
described as the ■ cords of the dorsal groove.' 
t This 'organ' is the intestine of Lesueur, and, as I have said above, is nothing but a ma, of blood-corpuscles 
t 
hypopharyngeal 
— — j j ^ , 
to be the lower parts of the peripharyngeal ridges. 
I have already said, renal organs. What Savigny calls their ducts seem 
