40 EMBRYOLOGY OF THE STARFISH. Part I. 



a degree, that the extremity of the ray is almost twice as broad as its base (PI. VI. 

 Figs. 10, 11, 12). The outline of the inner wall of the disk can be easily seen 

 through the limestone net-work. The pentagonal form, so different from that of the 

 adult, is still less like it when seen in profile (PI. VII. Fie/. 2). The abactinal area 

 rises like a high, rounded cone, supported upon the spines (p) of the edge of the 

 disk; the tentacles project far beyond the edge on every side (PI. VII. Fig. 2). In 

 fact, the regular rows of spines, their great size, the convexity of the disk, are 

 features so unlike our usual conception of a Starfish that, without closer examination,* 

 one would readily mistake this Echinoderm, at first sight, for a young Sea-urchin, like 

 the flat, conical Echinocidaris. 



The tentacles are longer than the rays, extending far beyond the edge in front 

 and on the sides. The pairs of tentacles move in every direction; but the odd 

 tentacle is always curved upward, and carried between the two middle spines of 

 the extremity of the rays. "When we see the Starfish in profile (PI. VII. Fig. 2), 

 the red eye -speck appears prominent near the edge of the disk, surmounted by 

 the up-turned tentacle (f t'), of a slight rosy hue. This manner of carrying the 

 terminal tentacle reminds us strongly of the way in which iEginopsis, as well as 

 the young of so many of our Hydroid Medusas, carry their marginal tentacles: 

 Nemopsis, Staurophora, Turritopsis, Willia. 



This is the most advanced stage of the young Starfishes (PI. VI. Fig. 11), 

 which I have succeeded in raising in confinement. When we compare this with an 

 adult, having long, slender-pointed rays, four rows of suckers, its surface covered 

 with pedicellariaa and water-tubes, surrounding individual spines, like so many wreaths, 

 we cannot fail to be struck with the astonishing changes of form which must still 

 take place to bring this pentagonal star to any shape resembling a slender five- 

 rayed Starfish. In fact, when we . remember how rarely embryologists continue the 

 study of the egg beyond the moment of hatching of the embryo, it is not to be 

 wondered at, that this same young Starfish should be introduced to us again and 

 again, in its different stages of growth, under half a dozen new names, both generic 

 and specific. It is only by a thorough knowledge of all the changes of form 

 through which these young embryos pass, from the first moment of their existence 

 till they are full-grown, that we can hope to remedy this evil. 



The next state in which our young Starfish is found is, when magnified (PI. VIII. 

 Fig. 1), even more different from the adult than the pentagonal state of PI. VI. 

 Fig. 11. The young Starfishes figured on this Plate (PI. VIII.) were all found 

 attached to roots of Laminaria, thrown up on the beaches, in the neighborhood, after 

 a storm; and from their different stages of growth, as compared with the oldest 

 Starfish raised from a Brachiolaria (PL VI. Fig. 11), specimens of which were also 

 found upon these roots, it is probable that the sizes here figured are one {Fig. 1), 



