MOLLUSCS. 



299 



Fig. 338. — JBoiis 

 pilata. 



each side. In Hermma the gills are more nuraerous, and the tentacles, which are 

 broad and flattened, are usually folded. Our New England species, H. cruciata, has 

 received its specific name from the cross-like marking of each gill. The 

 species of Montagua, of which we have over half a dozen forms, and 

 the closely allied Eolis, have a large number of gills arranged in trans- 

 verse rows upon the sides of the back. They are very active animals 

 (for nudibranchs) and are common on piles of bridges, among the roots 

 of searweeds, and on rocky bottoms. They lay their eggs in gelatinous 

 spirals with wavy margins, resembling a lady's frill in general appeai-- 

 ance. Frequently bright colors are present, making these among the 

 most attractive of marine objects. 



In Doto and allied forms the tentacles are retractile into cup-shaj^ed 

 sheaths, while the branchiae are most curious bodies covered with minute 

 papillse. Doto coronata, which extends from our shores to those of 

 northern Europe, is a handsome object. It is scarcely more than half 

 an inch in length, but, small as it is, there is room for spots of orange, pink, yellow, 

 carmine, purple, and white. Possibly one of our most striking forms is Dendronotus 



arhorescens, with its 

 curiously branching 

 gills, which, from 

 their thin, bushy ap- 

 pearance, have given 

 rise to both its gen- 

 e r i c and specific 

 names. This branch- 

 ing feature is also 

 seen in the tentacu- 

 lar sheaths which are 

 split up like the calyx 

 of a flower. The 

 general color is flesh- 

 red or brown. This 

 is one of the most 

 active of the naked 

 molluscs, and, when 

 confined in an aquar 

 rium, is scarcely ever 

 quiet. It lies on 



hydroids and sea^weeds, being especially adapted for creeping around upon them by 

 its long and slender foot. 



The genus Scyllea, which has the body expanded into two long lobes, bearing the 

 gills on either side, is interesting from the fine instance of mimicry it affords. It lives 

 upon the gulf weed {Sargassum) of the Atlantic and other seas, and with it is occa- 

 sionally drifted upon our shores. The large fields of this sea-weed which exist in the 

 tropical Atlantic have a fauna of its own, and among other forms are numbers of fishes, 

 crabs, shrimps, and the slugs now under discussion. Were it not for its protective 

 resemblance to the sea^weed on which it dwells, a resemblance embracing both form 

 and color, Scyllea pelagica would furnish many a fine mouthful for its voracious asso- 

 ciates, and the species would soon become extinct. 



Fig. 339. — De^idronotus arhorescens, bushy sea-slug. 



