CTENOPHORES OF THE ATLANTIC COAST OF NORTH AMERICA 45 
at a lower level, the 2 paragastric and 2 tentacular vessels. All of these 
canals are of slender caliber. 
The 4 interradial vessels (7, fig. 61, plate 12) fork near their aboral 
ends, and give rise to 8 adradial vessels (ad, fig. 61, plate 12). The adra- 
dial canals leading to the meridional subventral vessels are relatively 
long, but those leading to the meridional subtentacular vessels are 
very short. The subtentacular vessels, st, give rise to 4 short rows 
of combs and also extend outward and downward (oral-ward) beyond 
their points of origin, and then bend inward and finally outward along 
the middle of the broad sides of the body and at last join with the 4 
meridional subventral canals at the middle of the tips of the ribbon- 
like body. The oral forks of the paragastric canals also fuse with the 
meridional canals at this point, and in their course along the almost 
knife-edged oral side of the body one finds numerous, simple tentacles. 
The oral forks of one side of the body do not connect with those of the 
opposite side, and there is no ring-canal around the mouth. There are 
neither tentacles nor combs upon the narrow, lateral ends of the body. 
The 2 rudimentary, axial tentacles are each set within a deep sheath in 
the side of the body close to the side of the paragastric canals. 
The sexual products are developed throughout the entire lengths 
of the 4 meridional subventral canals under the combs of cilia. 
The young animal is transparent, but when old it often becomes 
violet with a beautiful greenish-blue or ultra-marine fluorescence (see 
‘Chun, 1880, Ctenophoren des Golfes von Neapel, p. 152). 
The embryonic development has been well described by Chun, 
1880, pp. 135-141. The larva passes through a Mertensia-like stage 
wherein the tentacular diameter is longer than the stomodeal axis, al- 
though as growth proceeds the stomodzal axis becomes so enormously 
extended that the body is reduced to the shape of a flat ribbon. While 
in the Mertensia stage there are about 4 ciliated plates on each of the 
meridional subventral and 1 ciliated plate on each meridional subten- 
tacular canal. The meridional canals and the paragastric canals at first 
end blindly, but their free ends extend outward and downward and finally 
fuse with the oral forks of the paragastric vessels. The larva is strik- 
ingly like the Cydippide and shows the evident derivation of Cestum 
from this order, but the general plan of the canal-system resembles that 
of the immature Beroide, in the separation of the peripheral canal sys- 
tems of the two sides of the body although in the mature Beroide a 
circum-oral canal develops in some species, and all of the meridional 
vessels become connected by a network of fused lateral branches. 
Cestum veneris is abundant in the Mediterranean and is also found 
in the tropical Atlantic. At Tortugas, Florida, it is not often met with, 
but can not be called rare. The so-called Cestum amphitrites Mertens, 
of the tropical Pacific, appears to be identical with the Atlantic and 
Mediterranean C. veneris, and Bigelow, 1904, appears to have described 
this form from the Maldive Islands, Indian Ocean, under the name 
Cestum pectenalis. Wagner, 1885, records the capture of Cestum veneris 
in the White Sea and this is the most northerly locality from which this 
‘Ctenophore has been reported. It was probably swept northward along 
the Norwegian coast in the Gulf Stream drift. 
