SURFACE FAUNA OF THE GULF STREAM. 15 
somewhat greenish tint, and connects at the base of the tentacle with the 
vascular system of the lower part of the mantle at the point of attachment. 
The cavity leading to the tentacular knobs is very slender (PI. X, Fig. 8). 
The smaller polypites (the feeding-reproductive polypites) occupy on the 
lower surface that portion of the mantle which covers the ring formed by the 
so-called white plate of Kélliker, round the base of the single central polypite. 
These polypites are sometimes seated in cavities of this white plate, and pro- 
jections of the plate itself also extend sometimes far up into the lower part of 
the small polypites. 
The white plate consists of an irregularly anastomosing system of needles 
and spurs, or of bars of greater or smaller size, leaving a series of openings 
for the passage of the tubules (Pl. VIII, Figs. 1, 1°; Pl. IX, Fig. 11). These 
tubules take their origin on the lower side of the disk, run in all possible 
directions between the interstices of the white plate, and come out as blind 
sacs on its lower side (Pl. XT, Fig. 1). Some of these tubules extend along 
the side of the small polypites (Pl. VII, Figs. 1, 2,4), while others follow the 
extension of the white plate (Pl. X, Figs. 4, 6), into the base of the central 
polypite some distance up its walls, forming a most delicate frill(Pl. X, Fig. 
4,7) of silvery radiating lines, extending towards the mouth of the central 
polypite. If this white plate is a kind of kidney, as Kolliker suggests, its 
openings lead outwards through the cavity of the central polypite, as well 
as through the openings of the smaller reproductive polypites, which are 
placed on the ring it forms round the central polypite (Pl. VIII, Fig. 1), and 
into the base of which this white plate extends a considerable distance. 
Although Kolliker calls it the “white plate,” it is in reality of a pinkish 
color toward the periphery, and blueish towards the interior edge, the whole 
of the part which lies within the base of the central polypite being of that 
color, The inner part of the ring of the white plate is composed of heavier 
bars, the edges only being spongy (Pl. XII, Fig. 15). 
The liver (Pl. VIII, Figs. 1, 1°, Z, 16) occupies the whole of the space be- 
tween the lower surface of the disk, the level of the white plate and the base 
of the central polypite. It fits closely into all the corrugations of the lower 
side of the disk, as well as into the upper ramifications of the white plate. 
It sends out a complicated system of radiating and anastomosing tubes from 
the centre towards the margin of the mantle, in which the circulation is kept 
up very actively (Pl. XII, Fig. 13). In younger specimens the radiating 
tubes are still quite simple (Pl. IX, Figs. 1-4; Pl. XII, Figs, 1-8). With 
