236 CTENOPIIOR^. Part II. 



end, where it merges into the cylindrical part of the tentacle. As the tentacular 

 fringes {Fig. l-j Z"^) are not to lie found upon this ridge, Init just at its distal tenui- 

 nation, and onward, — and, if we mistake not, the lasso-cells are absent, — it may be 

 proper to consider it as essentially a part of the disk, simply subservient to the 

 movements of the prehensile organ, which is prolonged from it. 



There are two distinct walls or layers, which constitute the body of the disk, 

 and which are continued, in the same relation, into the tentacle ; but the greater 

 proportion of this apparatus is composed of the inner layer {Fig. 87 / y' y" y"'), the 

 outer one {Fig. 15 and Fig. 87 /:*' /:?" ('i'") being comparatively a very thin stratum. 

 The thinnest part of the inner layer may be found about the proximate side (}'"') 

 of the two parallel chymiferous tubes {a to a'"), which jtenetrate to the apex (;'") 

 of the disk, where it occupies one half of their circumference, as a mere film 

 (;'"') of long, slender cells, identical Avith those which we have already pointed out 

 (pp. 223, 224) as forming the walls of the whole chymiferous system. On the solid 

 side {Fig. 87 ;') of these tubes and between them {Fig. 10 ;), this layer more or 

 less suddenly becomes very thick ; at the distal side of the apex (; ") of the tubes 

 the transition is comparatively gradual, as one might very naturally infer from the 

 form of the disk ; but at all other points the passage, from the filmy wall to the 

 highly incrassated core of the disk, is very alirupt, especially at the abactinal end 

 (;""), where it projects like a hook or nose. In the tentacles (/") again it loses 

 its Inilky proportions, whilst the outer layer gains the ascendency (within the 

 main stem of this organ the decrease is not so great as in the fringes) ; in the 

 former the inner layer forms a solid axis, occupying aliout two thirds of the 

 diameter of the tentacle, whereas in the latter {Fig. 13 d, Fig. 18 (/) it forms 

 but one third of the whole thickness. Along the median line of this layer, in 

 the fringes, there is a slender string {Fig. 13 c, Fig. 18 c) of matter Avhich is 

 much more transparent than the rest, and has the appearance of a canal ; liut no 

 distinct cavity could ])e detected. The course of the longer axes of the cells 

 constituting this layer is very simple. "Within the disk it is lengthwise {Fig. 15 a), 

 and in a general way parallel to the surface of this body ; and so, too, in the 

 tentacle and its fringes {Fig. 13 d). At the origin of the fringes {Fig. 15 /~\) 

 the cells of the main body (Z~) of the tentacle bend nearly at right angles upon 

 themselves, and enter at once into the former without any break ; they are as 

 directly continuous from the one to the other as from the disk into the tentacle. 

 When the tentacle is contracted it is transversely wrinkled, and in this condition 

 the cells which diverge at right angles into the fringes appear to traverse the 

 whole diameter of the main laA'er as if the_y were distinct liands, originating inde- 

 2iendently of the cells of the latter; and this deceptive a})pearance is all the more 

 heightened if a portion of the tentacle be cut away and laid out on a slip of 



