SEA-B UTTERFLIES. 3 2 1 



green color, which well adapt them to abiding among the sea- 

 weeds. In the intestines of many specimens which I have exam- 

 ined for that purpose I have found among fine grains of sand and 

 mold dubious remains of sea-plants and little shells of swimming 

 mollusk-larvse. 



Many sea-butterflies are naked, having their spindle-like bodies, 

 instead of shells, covered only by a sack-like skin. The laterally 

 fixed wings are sometimes drawn back into pockets, and over them 

 rises a roundish, somewhat depressed head-part, which is occa- 

 sionally provided with appendages bearing hooks or suckers. To 

 them belongs the above-mentioned violet-colored JPneumodermon 

 of the Mediterranean Sea, which, when danger is impending, 

 envelops itself in a white cloud of slime that is secreted in numer- 

 ous glands, but is soon exhausted. 



A species occurs in the northern seas which, together with a 

 little butterfly, Limacina arcbica (Fig. 8) — a species having a 

 somewhat spiral, transparent shell — comes into remarkable direct 

 relations with man. The little Limacinas appear in immense 

 swarms in the polar seas, and the not less numerous naked Cliones, 

 Clione borealis (Fig. 7), which are much larger and inflict griev- 

 ous destruction upon them. In the Mediterranean Sea the Cliones 

 are represented by the related genus, Clinopsis Krohnii (Fig. 6). 

 The polar voyager, Captain Halboll, once tried to bring some liv- 

 ing Cliones to Prof. Eschricht, in Copenhagen, for examination. 

 Knowing that they were carnivorous, he fed them with reindeer- 

 meat, which they ate greedily at first ; but, although he changed 

 the water frequently, he was not able to keep them alive more 

 than eight days, and had to bring them preserved in alcohol. But 

 Eschricht made a very satisfactory research upon them. 



The Limacinas eat little crustaceans, the Cliones eat the Lima- 

 cinas, and both are consumed by the ton by whales. The Green- 

 land whale appears to live almost exclusively on the two species 

 of sea-butterfly, which it has to swallow in immense quantities to 

 fill its capacious maw. It eats also other pelagic small fry and 

 crustaceans as side-dishes. 



These are only indirect relations in which the sea-butterflies 

 inhabiting all seas stand to man. But they are important enough. 

 Without whale-food, no whales ; without these, no blubber to 

 grease sailors' water-proof boots and overalls ; and without boots 

 and south westers, no* sailors and high-sea fishermen ; and with- 

 out whales, no whalebone, no parasols and umbrellas and corsets, 

 which were not worn by the beauties of ancient times, because 

 1 they were limited to the productions of the Mediterranean Sea, 

 where there are no Greenland whales. But chains of this kind 

 can be found everywhere. 



The older French naturalists — D'Orbigny, Pdron, Lesueur — 



VOL. XXXV. — 21 



