Chap. II. PHASES OF THE LAEVJ1. 43 



they approach the extremity of the ray; they are not open at the tip. The central 

 basal abactinal plate is still distinct from the others. 



The development of the pedicellarise around the base of the spines gives us no 

 clue as to the function which they perform in Starfishes (PI. VIII. Figs. 2, 3, 4). At 

 first a simple projection, they early assume the character of the head of pedicellaria3 

 without stems, the rounded swelling becoming conical, after which the fork of the head 

 begins to be distinguished. In Plate VIII. Figs. 2, 3, 4, we have the different stages 

 of the spines (p), and the pedicellarias {p',p"), found at their base. It was impossible 

 in these young Starfishes to discover the place of the madreporic body. 



From the oral side, these Starfishes (PI. VIII. Fig. 9) exhibit scarcely any differ- 

 ence from those of the stage last described, with the exception of the somewhat 

 more crowded ambulacra. There is a row of median ambulacral spines («'), quite , 

 small, defining the plates distinctly, as well as the presence of a very distinct row 

 of spines (u), the ambulacral spines, along the edge of the ambulacral plates. In 

 the most advanced of these Starfishes, we must specially call attention to the ab- 

 sence of a well-defined interambulacral system. The young Starfish is still eminently 

 ophiuroid in its most important embryonic features. 



Professor Sars, in his Norge's Echinodermer, has described a new genus, which 

 he has named Pedicellaster. I think there can be but little doubt, on comparing 

 the figure he has given of his Starfish and the different stages of our Asteracan- 

 thion, that his Pedicellaster will turn out to be the young of one of the species of 

 Asteracanthion of the northern coast of Europe. The single row of ambulacral 

 pores, the ocular tentacle, the arrangement of the pedicellarias, the size, all confirm 

 the idea of its being only a young. 



Successive Phases of Development of the Larvae of Starfishes. — Before applying the 

 information thus far obtained to the solution of more general problems, it may be 

 well to consider what are the normal stages of growth, at different periods, in the 

 history of our Starfish larvae. During the earlier stages of its existence, the young- 

 developed from the egg (PL I. Figs. 22-28) laid by one of our Asteracanthion has 

 no resemblance whatever to the future Starfish. This first condition we might call 

 the pyriform, or Scyphistoma stage; when it is simply a symmetrical radiate animal, 

 reminding us of earlier stages of Polyps and Acalephs. It then assumes the shape 

 of a dumb-bell, becomes slightly one-sided (PI. II. Figs. 2-19), and has, in its most ad- 

 vanced state, no other appendages but the simple crescent-shaped, slightly undulating, 

 vibratile chord (PI. II. Figs. 20-24). The simple straight digestive cavity is now 

 differentiated into three distinct regions. This second stage we might call the 

 Tornaria stage, from its resemblance to the Echinoderm larvaa, called Tornaria by 

 Miiller, in which all the parts of the adult larva are simply hinted at in the 

 most rudimentary form, and during which it is eminently cylindrical. Another well- 



