PYROSOMA.— A TAXONOMIC STUDY, BASED UPON THE 

 COLLECTIONS OF THE UNITED STATES BUREAU OF 

 FISHERIES AND THE UNITED STATES NATIONAL 

 MUSEUM. 



By Maynard M. Metcalf and Hoyt S. Hopkins, 



Oj Oberlin, Ohio. 



INTRODUCTION. 



The family Pyrosomidae is generally regarded as containing but one 

 genus Pyrosoma. There are, however, two very distinct groups in 

 the family, the Pyrosomata ambulata and the Pyrosomata Jlxata, which 

 might as properly be regarded as two separate genera. In this paper 

 we are treating them as subgenera, although it would be equally well 

 to give each group its own generic name. The members of the family 

 all have the form of free swimming, tubular colonies, and they all 

 emit a strong phosphorescent light. They are said to be the most 

 brilliantly luminous of all marine organisms. 



Pijrosorna was first described by Peron (1804), and was later more 

 thoroughly studied by Lesueur (1815). The earlier specimens known 

 came from the Atlantic Ocean and Mediterranean Sea, but many have 

 since been collected from all seas, with the exception of the Arctic 

 Ocean. About sixteen species and varieties are now known, including 

 the new forms described in this paper, whereas previous to the year 

 1895 only three had been described. In that year appeared Seeliger's 

 memoir, "Die Pyrosomen der Plankton Expedition," and this was 

 followed by important memoirs by Neumann and others upon collec- 

 tions made by different oceanographic expeditions. The anatomy, 

 embryology, and budding have been well studied, but little is known 

 of the behavior of the living animals or of their physiology. 



Our studies are based upon the remarkably rich collections of the 

 United States Fisheries Steamer Albatross in Philippine waters during 

 the years 1908 and 1909 and upon the extensive collections in the 

 United States National Museum, made almost wholly by vessels of 

 the United States Bureau of Fisheries, chiefly the steamer Albatross, 

 which since 1883 has been almost continuously engaged in oceano- 

 graphic studies. The Plankton, theGerman Deep-Sea and theGerman 

 South-Polar Expeditions all made important collections, but all of 

 these combined do not equal in number of types the collections of the 

 Albatross Philippine Expedition. We have had for study two hun- 

 dred and thirteen colonies, comprising thirteen species and varieties, 

 including all but four of the forms of Pyrosoma hitherto described, 



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