PELAGIC ANIMAL LIFE 



599 



Only exceptionally, and chiefly in the Antarctic, forms were found be- 

 tween 1500 and 1000 metres that in warm waters live at the surface. 

 The Salpae are individually most abundant in warm water, and in the 

 Atlantic we do not find a single species which is peculiar to the area 

 north of lat. 45° N. Apstein tells us that three species have been found 

 in the northern region, viz. Salpa fusifoi-mis, S. mucronata, and 

 5. :::onaria, but they really belong to warm waters and have been carried 

 north by currents (see Fig. 447). The genus Cydosalpa comprises 

 typical warm-water forms. 



The genus Dolioliiin is also, according to Neumann's ^ treatise on 

 the " Valdivia " collection, chiefly a warm-water form exceedingly 

 sensitive to changes of temperature. Dolioliim kroJini, D. tritonis. 



Fig. 447. — Distribution of Salpa fcsiformis. 

 (From Apstein.) 



D. mulleri, and D. gegenbaiiri are the species which go farthest north in 

 the Atlantic. 



The genus Pyrosoma (Fig. 448) has from the earliest days of 

 oceanography attracted the interest of man, to a great extent on 

 account of the strong phosphorescent light emitted, the name meaning 

 " fire-animal." The individuals are aggregated into cylindrical colonies, 

 which may attain an enormous size (several yards long). Some occur in 

 the surface-waters, some in deep water. 



In the narrative of the "Challenger" cruise, Sir John Murray, 

 describing the voyage from the Bermudas to the Azores, writes as 

 follows : — " On the 25th (of June) a very large colony of a new species of 

 Pyrosoma was captured in the trawl. The cylinder was 4 feet 2 inches in 

 length and 10 inches in diameter, closed at one end, and as in the 



Neumann, Wiss. E7-geb. Valdivia-Expediiion, Bd. 12, 1906. 



