428 SUPPLEMENT 
place of testicles. 'The ovaries are towards the base of the 
body. We sometimes find between this base and the mantle, 
an immense quantity of eggs, forming a thick stratum of 
yellowish matter, which covers the back of the animal. The 
gills are little conical leaflets, of a soft substance, attached to 
the base of the tentacula in such a manner, that there are as 
many pairs of threads as there are pairs of tentacula. But 
these threads are directed in a contrary way, that is, towards 
the back, and inclined against the body under the mantle. 
The nervous system likewise presents some peculiarities. 
The brain is situated cross-wise on the mouth. Four nerves 
repair to the muscles which border this organ, and to the 
stomach. ‘Two other cords embrace the cesophagus, approxi- 
mate to form a ganglion, and then rise, pressed one against 
the other between the tentacula, each pair of which receives 
a nervous filament detached from the principal cord, without 
forming any enlargement. 
We have purposely entered into some detail respecting 
the organization of the anatife, because it presents many 
peculiarities, when compared with that of the other mollusca. 
Those concerning the nervous system, and the gills, are taken 
from the Comparative Anatomy of M. Cuvier. 
Fixed by its fleshy tube, and unable to move but by the 
elongation and contraction of this tube, and by its flexion in 
all directions, the anatifa presents but little that is remarkable 
in the history of its manners. The medium in which it is 
immersed, is filled with substances, which serve it as aliment. 
This was necessary for its preservation, since it is incapaci- 
tated to go in search of food. To obtainit, it is sufficient that 
the animal should determine towards its mouth, a current of 
the surrounding fluid, by means of its multiplied arms. 
Most of the species live in groups of fifteen or twenty, more 
or less. They prefer such situations as are beaten by the 
waves, and when attached to the keel of a vessel they 
