PELAGOSPH^RA, A LARVAL GEPHYREAN. 



HAROLD HEATH. 



In 1905 Dr. Pio Mingazzini published an account^ of a gephy- 

 rean worm taken at a depth of 4,500 meters during an expedition 

 of the Duke of Abruzzi in the neighborhood of Aukland. It is 

 described as a spherical transparent organism, of about 6 mm, 

 diameter, with a decided resemblance to certain sipunculid larvae. 

 However, as the author considered it to be an adult, it was 

 placed in a new genus for which he states a new family may 

 have to be created. 



Spengel ^ chiefly on the basis of Sipunculus larvae taken in the 

 Bay of Naples, declares without hesitation that the animal in 

 question is a larval form differing in a few minor details from 

 other well-known types. The so-called gonad may well be the 

 glandular appendages of the oesophagus noted in the young of 

 several species. 



During the past year two individuals, belonging to this pro- 

 posed genus, have been taken in the surface plankton of Monte- 

 rey Bay, Cal., and there is no doubt they are immature, the 

 "gonadi" being, as Spengel surmised, glandular appendages of 

 the pharynx. Nevertheless they present a number of features 

 of considerable interest that are herewith described in some de- 

 tail. 



Both, apparently belonging to the same species, are spherical 

 and measure 2.5 and 3.2 mm. respectively. In life the body 

 wall was almost transparent, the muscles, especially those radia- 

 ting from the mouth opening, appearing much as they do in 

 Doliolum or Salpa. The alimentary canal was light yellow and 

 the nerve cord and especially the brain were more opaque and 

 fairly distinct. 



The most prominent structure of these animals is the alimen- 

 tary canal, which in its general features resembles that of the 



' "Un Gefireo pelagico: PelagosphcBra aloysii n. gen. n. sp.," Rendic. Accad. 

 Lincei, cl. sc. fis., mat. nat. {$), Vol. 14, pp. 713-720. 



^ "Eine verkannte Sipunculus-Larve," Zool. Am., Bd. 31, 1907 



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