EXPLANATION OF THE PLATES. 



(5) 



n', tLe abactinal end of tlie interambulacral motor bands, 

 n', the inner face of n. 



n^, the actinal end of the interambulacral motor bands. 

 n', the tentacular motor system. 



p to p', the lateral cellulo-motor system ; p where the wings 

 from two opposite sides meet ; p^ those cells which pass 

 from the tentacular sockets to P, P, I*, P, and C and 

 G ; p- the profile of the inner face of the wings ; 

 p' the superficial termination of this system, along the 

 borders of ?7i'. This system is shown only on one half 

 of the figure, in order to avoid confusion. 

 '/, '/, the four main trunks from which the eight radiating 

 chymiferous tubes arise. It should be noticed, that these 

 tubes are not strictly in the same horizontal plane, since 

 their respective position varies more or less in the differ- 

 ent contractions of the body, and those on one side 

 are successively higher than those of the opposite side 

 in the alternate contractions of the opposite halves of 

 the body, wliich regulate the general circulation of the 

 nutritive fluid, 

 r, r', the coeliac tubes following the digestive cavity. 

 They arise from the main horizontal tube, and extend 

 to the margin of the mouth, following the middle of 

 the flat surface of the digestive cavity. 

 r", entrance to r, r'. 



s, the eight epidermic narrow bands of fi.\ed ciliate bodies 

 which pass from the abactinal ends of the rows of loco- 

 motive flappers to the base of the cap over the peduncu- 

 lated globular eye <!. 

 t, t^, the radial cellulo-motor system around the a.xial funnel, 

 u, rows of locomotive flappers. 

 V, vertical chymiferous tubes, which accompany, on the 



inner surface, the rows of locomotive combs. 

 d', the same as u in a contracted state. 

 10, basal line of the locomotive flappers, 

 tt-", the sub-ambulacral motor cells, probably continuous with 



those which constitute the flappers. 

 X, ganglions ? These swellings are more or less eva- 

 nescent, and appear rather to be small bodies caught 

 in the symmetrically arranged folds of the chymiferous 

 tubes, 

 x' r', cells of the interambulacral system on the borders 



of the sub-ambulacral system x'. 

 y, ganglion-like bodies, arising probably from the accumu- 

 lation of granules in the contracted state of the ver- 

 tical chj-miferous tubes when the circulation has ceased, 

 o, chj-miferous tubes of the tentacular apparatus, 

 a', the opening through which the vertical chymiferous tubes 

 of the tentacle open into the main horizontal chymife- 

 rous tubes between their main forks. 



a'' a'", the same as a, one on each side of the tentacular 

 base. 



/3, elongated disk from which the tentacles arise. 



[)', margin or outer wall of (i. 



j3", outer wall in profile at the margin of y. 



ft'", outer wall at the thickest part of the disk. 



7, the longitudinal furrow of the disk (in fig. ia), or the 

 keel-like prolongation of the inner la}er f)f the disk 

 between the tentacular tubes, to which it is a wall. 



y', the inner layer of the tentacular base. 



y", the apex of the disk. 



(5, eye-sj)eck in the centre of the circumscribed area. 



rf', globular cavity containing the eye-speck 6. 



c, the shallow, oblong furrow of the circumscribed area lined 

 with vibratile cilia. 



£*, raised line following the inner outline of f, probably the 

 analogue of that row of fringes so conspicuous around 

 the circumscribed area in some other genera of Beroid 

 Medusa;, and particularly distinct in the genus Idyia. 



r, another line, parallel to the former and within it, the 

 special nature of which I have failed to ascertain. 



f, the openings, cceliac apertures, of the two bulbs of the 

 vertical funnel, through which the fiecal matters are 

 from time to time discharged. 



e, the tubercle upon which the eye-speck 6 rests. 



t, K, concentric swellings connected with the ganglion of 

 the eye-speck, stretching in the direction of the longi- 

 tudinal diameter of the circumscribed area. 



A, four ganglionic swellings within the inner of the swollen 

 margins near the ganglion of the eye-speck, the nature 

 of which I have also failed to determine. 



Figs. 1-12. Lasso-cells from the fringes of the tentacles. 

 Fig. 1 is magnified 500 diameters, the others 200 di- 

 ameters, by means of Spencer's one fourth inch ob- 

 jective and Tolles's solid ocular, number E. In all 

 these figures a is the wall of the cell, b the lasso, c 

 the base or point of attachment of h, d the free 

 end of h, e the mouth of the cell, / the granular 

 covering of a. 

 Fig. 1. A closed lasso-cell as seen with 500 diameters. 

 Fig. 2. The same as fig. 1, magnified as above, with the 



granular coating in profile. 

 Fig. 3. An open cell, partially contracted, and'the lasso 



out. 

 Fig. 4. Still more contracted than fig. 3. 

 Fig. 5. The wall almost entirely decomposed. 

 Fig. 6. The lasso forcing its way through the closed 



mouth. 

 Fig. 7. Foreshortened view of fig. C, the granular coating 

 in profile. 



