SEAS OF FLAME. 89 



fifteen miles in extent. Some observed in the South Atlantic 

 had the nucleus tinged with a brilliant red light. Very simi- 

 lar to Salpa is Doliolum, which seems to burn with a vivid 

 green light scattered over the entire body, and is one of the 

 emeralds of the sea. In the very lowest order ( Copelatce) of 

 the Tunicates, we find an interesting, indeed remarkable, light- 

 giver, the Appendicularia (Plate XVI., Fig. 3). It resembles 

 a tadpole with quite a long tail, retaining in its adult life 

 features that only characterize the larvae of others of the 

 group. Professor Agassiz has noticed two specimens on 

 the New-England coast, and they are very common in both 

 tropical and temperate waters of various regions. 



Some of the species are veritable house-builders, forming 

 a gelatinous protection covering called a test. This habita- 

 tion, if so we may term it, is formed or secreted with con- 

 siderable rapidity, and is quite an elaborate affair ; having 

 two front chambers and a middle one large enough for the 

 tail to move with ease. Curious to relate, this transparent 

 residence is, according to Filhol, only used a few hours, 

 being then deserted and another formed; so that its life 

 would seem to be spent in making houses and deserting 

 them. 



The light of certain Appendicularice is almost as remarka- 

 ble as that of the Pt/rosomce, in the variety of its coloring ; 

 one, according to Giglioli, appearing first red, then blue, and 

 finally green. The seat of the luminosity, which appears in 

 intense flashes, was the central axis of the taiL, or caudal 

 appendage. Between Montevideo and Batavia in the South 

 Atlantic, this naturalist observed many of these little crea- 

 tures, nearly all of which showed these tri-colored favors; 

 and in the Indian Ocean some were seen emitting white, 



