350 SUPPLEMENT 
plants in general abound. ‘Their motion is slow; they creep 
along with their tentacula and gills very much spread out, by 
means of the broad disk, which occupies their entire abdomen, - 
either on submarine bodies, or at the surface of the water in 
an inverted position. On the slightest contact they draw in 
their tentacula, and even in a great measure their gills, which 
have many relations of structure with the former organs, and 
gather up their bodies, much after the manner of the slugs. 
It was generally believed that they fed on living animal sub- 
stances, and among others upon oysters, and other fixed 
conchyliferous mollusca, whose shells they pierced by means 
of their sort of tongue. But M. Dupont de Nemours assures 
us that their nutriment consists in sea-weed. ‘Their mode of 
sexual intercourse is altogether unknown. ‘Their spawn is in 
the form of gelly, adherent to submarine bodies. 
As to the subsequent genera, down to scyllee, their 
habits are either utterly unknown, or may be presumed to be 
analogous to those of doris. 
The Scyllez, like the preceding, are hermaphrodites ; they 
are little pelagian animals, which seldom visit our coasts, but 
are not rare upon the masses of fucus in the Atlantic Ocean. 
They live, as it would seem, in the depth of the waters, where 
they creep upon the stems of fucus, as the canaliculated form 
of their foot would indicate. It is probable, however, that 
they can swim with equal facility, by means of the foliaceous 
appendages with which their body is provided, and especially 
the two branchial pairs. ‘Their other manners and habits are 
altogether unknown, but, in all probability, they differ little 
from those of doris and other neighbouring genera. 
Very little is known respecting the manners and habits of 
GLAUCUS, and the remaining genera of this order. We 
merely learn from Dupont and other observers, that they are 
found only in the high seas at a considerable distance from 
the shore, and that they often remain at the surface of the 
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