c»: 



EXPLANATION OF THE PLATES. 



project above. The Starfish in this condition is at 

 the point of resorbing the larva, and of closing the 

 actinal and abactinal areas. 



The young Starfish after the Brachiolaria has 

 been resorbed. 



Fig. 1. A young Starfish seen from the aetinal side ; 

 the anal and oral clusters of arms of the Brachio- 

 laria appear like small knobs, placed on opposite 

 sides of the new mouth. The future rays are mere 

 lobes, and are not symmetrical. 



Fig. 2. The same embryo seen from the abactinal side, 

 to show the arrangement of the net-work of lime- 

 stone meshes. 



Fig. 3. A more advanced embryo, in which all traces of 

 the appendages of the larva have entirely disappeared. 

 Each side of the pentagon of suckers is a rosette made 

 up of seven loops ; the limestone particles are deposited 

 so as to project at the angle of the arms between these 

 loops. The mouth is movable, the pentagon is not 

 closed, and the Starfish is not yet symmetrical ; the 

 shape of the different rays is not identical. 



Fig. 4. The same embryo seen from the abactinal side, 

 showing the arrangement of the successively formed 

 rows of rounded spines and of the plates. The two 

 ends of the open pentagon have approached nearer 

 than in Figs. 1, 2; the outline is not yet regular. 



Fig. 5. Magnified view of one of the ambulacral tubes, 

 with its rudimentary tentacles. 



Fig. 6. The young Starfish, in which the two pentagons 

 have almost closed, and been brought into parallel 

 planes. There has been a great increase in the size of 

 the cut between adjoining rays; the spines also have 

 grown longer and more pointed; the limestone points 

 of the angle of the rays have advanced nearer the 

 centre. The Starfish is not quite symmetrical, nor 

 are the arms exactly alike. 



Fig. 7. The same embryo, from the actinal side, shows 

 the great increase of the ambulacral system, the ten- 

 tacles being distinct pouches on each side of the main 

 tube. The basal tentacles of one system are much 

 further apart than all the others, and this is the last 

 indication that the ambulacral pentagon is not closed. 



Fig. 8. A more magnified view of the actinal side, when 

 the ambulacral pentagon is entirely closed, and the 

 Starfish has become symmetrical, and all the basal 

 suckers are equally distant. 



Fig. 9. The ambulacral system of one arm, when con- 

 fined by the circle of limestone which has been formed 

 round each ambulacral system ; the two first pairs 

 of tentacles begin to develop disks ; they become club- 

 shaped; the three terminal tentacles are still closely 

 connected, and show no sign of any disk. 



Fig. 10. An abactinal view of one ray and the centre 

 of a young Starfish, in which the spines project far 

 beyond the edge of the disk. The arm-plates and the 

 inter-radial plates have become connected by a narrow 

 bridge. The limestone rods are so much thickened 

 by additional deposits, that they form elliptical cells 

 which have entirely lost the polygonal character of 

 the younger stages. 



Fig. 11. One arm and a portion of the centre, from 

 the abactinal side, of the most advanced of the young 

 Starfishes which have been raised by artificial fecun- 

 dation. The spines are very prominent, long, some- 

 what spreading, and becoming even fan-shaped. The 

 limestone cells are gradually assuming the charac- 

 ter of the limestone cells of the adult, small cells 

 within larger ones ; the cut between the rays is very 

 deep. 



Fig. 12. The same young Starfish as Fig. 11, seen from 

 the actinal side ; the three pairs of tentacles have 

 suckers ; the deposit of limestone of the actinal area 

 having the same cellular structure as that of the 

 abactinal area, though formed by the increase of 

 small cells instead of rods. This Starfish also shows 

 the position of the madreporic body, immediately on 

 the edge of the disk of the lower side ; the eye is very 

 prominent at the base of the odd terminal tentacle. 

 The young Starfish, Figs. 11, 12, is about four months 

 old. 



PLATE VII. 



Fig. 1. Two rays and the centre of the Starfish, PL 

 VI. Fig. 10, seen from the actinal side. All the 

 tentacles are encased separately by the limestone de- 

 posit of the actinal region. The tentacles have grown 

 so long that they extend beyond the edge of the arm. 

 The pair of terminal tentacles has, as yet, increased 

 but little in comparison to the other pairs. The odd 

 terminal tentacle has, at its base, a bright carmine 

 spot, the eye, which appears about this time. The 

 mouth, limited by the limestone deposit, takes the 

 shape of a pentagonal opening; the ambulacral tube 

 is concealed. 



Fig. 2. The same Starfish as PL VI. Fig. 11, seen in 



