110 CLASS III. 
greater part of them have no connexion with these canals, or with 
the central polyp, but lateral branches of the vessels open into their 
pedicles, so that they at once give the product of digestion to the 
vascular system. In Porpita the lesser polyps open into liver-canals 
and not into vessels. 
The generative organs are seated, as clusters of minute bodies, on 
the pedicles of the smaller polyps. They become transparent and 
pyramidal, and having gradually assumed the medusan form are 
detached. They were first noticed by Dette Cutasn, Descriz. tv. 
p. 107, Tay. 146, fig. 10, 12. The sexual germs are formed on the 
wall of the radiating vessels. Huxtry, GEGENBAUER, |. 1. . 
The prehensive organs are placed around the lesser polyps on the 
horizontal margin of the mantle. They are hollow and open into a 
vessel like the lesser polyps. They have no special nettle-nodes, but 
numerous scattered thread-cells. 
The air-canals were discovered by Kroun ; they are minute vessels 
which pass from the innermost air-spaces of the horizontal cartilage, 
perforate the mass of the liver, and reach the walls of the polyps 
where they appear to terminate by closed extremities. They are 
most numerous in Porpita. See KoELiiKer Die Siphonoph. pp. 46— 
64. | 
Velella Lam. A semi-orbicular crest, compressed, containing a 
cartilage within, placed obliquely above the disc. Marginal ten- 
tacles simple. 
Sp. Velella spirans, Medusa velella L., Holoth. spirans Forsx. Icon. Rer. 
natur. Tab. Xxvi. fig. k, Armenistariwm velella Costa Ann. des Sc. nat. 
sec, série, Tom. Xvi. Pl. 13, fig. 3, (figure of the vessels from the stomachs 
on the inferior surface of the cartilaginous disc), in the Mediterranean. 
According to Forskau the French sailors call the animal Vallette: they 
eat it fried with flour and butter. The name Velella appears to be derived 
from velum and from the crest, which like a full-spread sail, adorns the 
upper surface. The beautiful blue colour of the animal is imparted to the 
water in which it is examined, but disappears in spirit of wine. During 
life the creature is not unattractive (‘‘non invenusta est quantum vermt 
licet,” Forsx. Deser. Animal. p. 105) ; see the coloured figure of LESUEUR 
in PERON, Voyage aux terres austr. Pl, xxx. fig. 6. (This species is from the 
Tropical Seas, Velella scaphidia PERon). ‘For the other species, not easily 
to be distinguished, of this genus, consult chiefly EscuscHoirz Syst. der 
Acalephen, s, 168—175. 
Subgen. Rataria Escuscu. Crest membranous, placed longitudi- 
nally on the disc. 
