SUEFACE FAUNA OF THE GULF STREAM. 15 



somewhat greenish tint, and connects at the base of the tentacle with the 

 vascular s^'stem 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 KoUiker, 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 pol^-pites. 



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 (PI. VIII, Figs. 1, V'; 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 (PI. XI, Fig. 1). Some of these tubules extend along 

 the side of the small polypites (PI. VIII, Figs. 1, 2, 4), while others follow the 

 extension of the white plate (PI. X, Figs. 4, 6), into the base of the central 

 polypite some distance up its walls, forming a most delicate frill (PI. X, Fig. 

 4, f) of silvery radiating lines, extending towards the mouth of the central 

 poljpite. If this white plate is a kind of kidney, as Kolliker suggests, its 

 openings lead outwards through the cavity of the central polyjiite, as well 

 as through the openings of the smaller reproductive polypites, which are 

 placed on the ring it forms round the central polypite (PI. VIII, Fig. 1), and 

 into the base of which this white plate extends a considerable distance. 

 Although Kulliker 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 (PI. XII, Fig. 15). 



The liver (PI. VIII, Figs. 1, 1", /, 16) occupies the whole of the space be- 

 tween the lower surfiice 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 (PI. XII, Fig. 13). In younger specimens the radiating 

 tubes are still quite simple (PI. IX, Figs. 1-4; PI. XII, Figs, 1-8). With 



