VELELLA. 107 



Fam. VELELLIDiE. 

 Genus VELELLA {Lamarck). 



The flattened pneumatocyst, which has more or less the form of a parallelogram, is 

 provided with a diagonal vertical crest. The tentacles are simple. 



Under the head of Holothuria spirans, Forskal (' Descriptiones,' p. 104, and 'Icones,' 

 tab. xxvi, fig. k, and k^ to /t') gave the first, and, at the same time, the best, concise scientific 

 account of a Velella extant. He was acquainted with the concentric chambers of the 

 pneumatophore, and with the fact that air is contained in them (" Nucleus annulis ovatis 

 concentricis." ..." In ejusdem nuclei annulis bullae aeris residui se manifestant vario 

 motu." ..." Hand raro fundum vasculi petiverunt emisso prius acre") ; being, in these 

 respects, far in advance of some of his successors. The descriptions of Bosc (' Histoire 

 Naturelle des Vers,' 1802); of Leach ('Tuckey's Voyage,' 1818, p. 419); of Chamisso 

 and Eysenhardt ('De Animalibus quibusdum,' Nova Acta, 1821); of Quoy and Gaimard 

 (' Voy. de I'Uranie, Zoologie,' 1824, p. 586) ; of Eschscholz (' System,' 1829) ; and of Lesson 

 ('Voyage de la Coquille, Zoologie,' 1830, t. ii, part 2, p. 48); contain no additions of 

 importance to the facts which Forskal had made known. 



De Blainville ('Actinologie,' 1834, p. 306) threw out the suggestion tliat the " Batariu" 

 of Eschscholz would turn out to be the young of VeleUa, a surmise which has proved correct. 

 Delle Chiaje ('Descrizione e Notomia,' tomo 4'°, 1841, pp. 105-8) figures and describes at 

 some length the vascular system. He points out the communication of the chambers of 

 the pneumatocyst with one another, and notices the gonocalyces, which he suspects to 

 be the genital organs. 



M. Hollard (" Sur I'Organisation des Velelles," 'Annales des Sciences Naturelles,' 1845) 

 endeavoured to prove that the small polypites or gonoblastidia of VeleUa are "aquiferous 

 tubes," and not digestive organs. On the other hand, he is the first to have pointed out 

 very distinctly the nature of the liver (though Delle Chiaje called it "fegato"), and, 

 apparently unacquainted with Delle Chiaje's work, he draws particular attention to the 

 gonocalyces, which he considers to be ovaria. The thread-cells which they contain he 

 takes for embryonic VeleUa, while the yellow corpuscles are ova less advanced. 



Ki'ohn (" Notiz iiber die anwesenheit eigenthiimlicher Luftkaniile bei VeleUa und Porpifa," 

 Wiegmann's 'Archiv.,' 1848) confirmed Delle Chiaje's statements as to the communication 

 between the chambers of the pneumatocyst, and at the same time communicated the 

 important discovery of the existence of tubular prolongations of the under wall of the 

 pneumatocyst containing air. Krohn adds a fuller account of the liver than had been given 

 by either Delle Chiaje or Hollard. 



