12 CTENOPHORES OF THE ATLANTIC COAST OF NORTH AMERICA 
dzum also is wide and flat and is between one-half and one-third as long 
as the long axis of the ctenophore. The funnel-cavity, or mid-region of 
the central entodermal part of the gastric system, sends out 2 wide 
paragastric branches, and also 2 canals to the bases of the tentacles, and 
it also gives rise to 4 interradial side branches, each one of which 
bifurcates, thus giving a canal to each of the 8 rows of ciliated plates. 
The gelatinous substance is transparent and glassy, while the tentacles 
and stomodeum are milky, or dull orange yellow or brownish orange. 
Fic. 5.—Pleurobrachia pileus; view looking down upon apical sense-organ 
at aboral pole of the animal. 
Lettering as in fig. 4. e, ova in meridional canals under ciliary combs; s, sensory 
tracts from apical sense-organ to rows of combs; to, opening of tentacle-sheath. 
The development has been studied by A. Agassiz, 1865, 1874. In 
common with that of other ctenophore, it is a simple metamorphosis. 
When young the tentacular diameter is about twice as great as the sagit- 
tal and the body is thus compressed laterally as in Mertensia. The combs 
of cilia make their appearance as 4 double rows of simple, hair-like lashes; 
