A TAXONOMIC STUDY ON PYROSOMA METCALF AND HOPKINS. 223 



tract. Its dorsal wall is greatly elongated, the ventral one much 

 shorter, and as a result of this the aperture opens obliquely ven- 

 trally, that is, in the direction of the closed end of the colony. We 

 find this to be true on examining the zooids in place in the colony, 

 although the test projects so far beyond the edges of the cloaca that 

 it quite obscures the real direction of the opening. A long, sharp 

 tentacle surmounts the dorsal rim of the cloacal opening. In length 

 (2-3 mm.) it may exceed the breadth of the aperture. 



Occurrence and distribution. The species is found in the Atlan- 

 tic, Indian, and Pacific Oceans. Our specimens are the first ones 

 reported from the Pacific Ocean; there are two of these, both from 

 the vicinity of the Philippine Islands. 



Specimens of Pyrosoma spinosum were obtained by the Albatross 

 during the Philippine Expedition of 1907-1910, as follows: 



D. 5613, Buka Buka Island, Gulf of To mini, Celebes; November 

 20, 1909; 752 fathoms; surface temperature 84° F. ; one specimen. 



D. 5631, Dowarra Island, south of Patiente Strait; December 2, 

 1909; 809 fathoms; one specimen, Cat. No. 6407, U.S.N.M., also Cat. 

 No. 6630, including 50 or more zooids from the same specimen as 

 Cat. No. 6407. 



One specimen, Cat. No. 6406, U.S.N.M., off the Massachusetts coast 

 at station D. 2228, latitude 37° 25' N., longitude 73° 06' W.; Sep- 

 tember 11, 1884; 1,582 fathoms; surface temperature 77° F. 



It seems probable that P. spinosum attains a larger size in the 

 Atlantic than in the Pacific Ocean ; and it seems certain that Pacific 

 specimens come to sexual maturity earlier. Kruger (1914) found no 

 gonads in the specimens which he describes as P. agassizi, but which 

 we take to be P. spinosum. His largest colony was over a meter in 

 length and about 10 cm. in diameter. Our largest Pacific specimen 

 is not more than 5 cm. in diameter (dimension of a fragment), yet 

 its zooids contain mature gonads and well-developed embryos. 

 According to other descriptions, there have been no embryos found 

 in Atlantic specimens of this species, although colonies of over one 

 meter in length have been reported. The very large colonies (4 m.) 

 from the Indian Ocean (Bonnier and Perez, 1902) were not closely 

 studied in this connection. It is natural to ask, is this difference in 

 size due to environmental conditions affecting growth (temperature, 

 abundance of food, and the like), or can it be that there are two 

 races of this species. 



Subgenus Pyrosomata Ambulata. 



Budding. The production of buds is accomplished as in the 

 Pyrosomata fixata, by means of a proliferating stolon formed at the 



