MOLLUSGA. 79 
foot to move upon, and their food is either vegetable or animal, some pre- 
ferring one kind and some another. 
Fam.1. Doridide. Yn this family the branchial plumes surround the 
vent in the form of a flower, situated upon the upper surface towards the 
posterior extremity (pl. 77, jigs. 16,17). The upper part is composed of 
a kind of large mantle, the jaws are corneous, the tentacles four in number, 
two dorsal and two labial. The dorsal tentacles and the branchiz are 
sometimes retractile. 
Doris includes many species whose brilliant coloring renders them con- 
spicuous objects. The dorsal tentacles have transverse ridges variously 
disposed in the different species; the branchiz are subdivided in a regular 
manner, but not uniformly in the different species. The eggs are deposited 
to the number of several thousand in a ribbon-shaped mass attached by its 
edge to extraneous objects, and wound in a spiral, varying from one to five 
or more turns. These animals live upon stones and marine plants; they 
move very slowly, and are not much addicted to locomotion. The length 
varies from about half an inch to six or seven inches. 
Fam. 2. Tritoniide. In this tamily there is a membranous veil or 
expansion in front, above the mouth (pl. 77, jig. 2); the branchize are in 
two longitudinal rows, and laminated, plumose, or papillate; two dorsal 
retractile tentacles. Zretonza (pl. T4, fig. 20), Tethys (pl. 77, fig. 2). 
Fam. 3. Holidide. “ Branchie papillose or branched, arranged on the 
sides of the back; stomach simple.” (Alder and Hancock.) These authors 
divide this family into two sub-families, Malibeinw and Eolidine, to 
which Glaucine may be added. The first contains the genus Dendronotus, 
of which D. arborescens, Muller, is found upon both sides of the North 
Atlantic. It is beautifully figured from specimens taken at Boston, by Mr. 
Couthouy, in the Bost. Jour. Nat. Hist., vol. v. Dr. Gould compares its 
branchiz to some fifteen or twenty widely and numerously branched plants. 
See his Invertebrata of Massachusetts, pp. 4-7, for descriptions of various 
species in this order. 
In Zolis the branchie are elongated papille resembling short cords 
arranged in longitudinal rows, and sometimes so numerous as to cover the 
back entirely. Holts salmonacea of Couthouy has about a hundred of them. 
They are frequently tinted with several bright colors, when they add much 
to the beauty of the various species. 
Glaucus has the branchie (which are used in swimming) in symmetrical 
pairs upon each side, each being a wing-like projection, with the margin 
fringed with numerous filaments. There are three or four pair, according 
to the species, the anterior being the largest, and the remaining ones 
becoming gradually smaller. Deshayes doubts whether these organs are 
branchiz, since they are cast off by the animal when disturbed; and 
indeed Couthouy expresses the same doubt in the case of Eolis, from which 
they can be cast off, and, when cut off, the animal does not seem to suffer 
much. He regards them as accessory to the general surface in the operation 
of oxygenating the system. ‘The papillz in one species dissected by Alder 
and Hancock contain a hepatic gland in the middle, and a circulation of 
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