Boone, Coelenterata, Cruises of "Eagle" and "Ara," 1921-28 37 



Family: PHYSALIIDAE. 



Genus : PHYSALIA Bosc. 

 Physalia physalis (Linne) Schneider. 



Type : Collected from the coasts of Santa Catharina, Brazil ; deposi- 

 tory not stated. Possibly St. Petersburg, Russia? 



Distribution : Pelagic in the West Indian region and Gulf Stream 

 and the tropical Atlantic Ocean as far as the Azores and Canary 

 Islands. 



Material examined: Two specimens, pelagic at Sombrero Light, 

 Florida, March 4, 1923 (coU. no. 140), collected by the "Ara." 



Color : The float is pearly with a bright bluish tint, varying to rose 

 color; the crest is margined with decided rose color and streaked 

 below with rose. The appendages are opaque milky white with a 

 bluish tinge. 



Discussion : Physalia physalis is the largest, best known, and most 

 remarkable of the American siphonophora. The air-sac is pear-shaped 

 with a conspicuous crenulated crest on the upper margin, which acts 

 as a sort of sail. Pendant below the air-sac are three types of hydrae ; 

 the large, locomotive hydrae which arise from a hollow stem that 

 communicates with the cavity between the inner and outer wall of the 

 air-sac ; outwardly the stem divides into three or four bunches of large 

 hydrae which are placed on the windward side of the air-sac. Similar 

 but definitely smaller clusters of hydrae occur on the lee-side. When 

 the animal is storm driven, these larger tentacles can stretch forty 

 to fifty feet in an effort to maintain the animal's safety. The feeding 

 hydrae are scattered along the lee-side of the bag, and are of two 

 kinds, large and small, clustered in bunches, each bunch arising from 

 a common stem that communicates with the chymiferous cavity of the 

 air-sac. The food is digested within these hydrae which have no tenta- 

 cles. The third types of hydrae are very small, forming large clusters 

 which are suspended among the feeding hydrae. The medusae buds, 

 which arise singly either from the base of these hydrae or adjacent 

 stems, are male or female, very similar to those of Tubularia. 



References: Holothuria physalis Linne, Syst. Nat., p. 657, ed. X, 

 1758. 



Physalia physalis Schneider, Zool. Anz., vol. 21, p. 190, 1898. — H. B. 

 Bigelow, Mem. Mus. Comp. Zool., vol. 38, p. 352, 1908-09 (with 

 synonymy from Linne to date). 



