OUTLINE OF THE YOUNG STARFISH. 53 



y, //'), the dorsal tubes (PL VlJi. Flfj. 10, d" d") are found arranged 

 in greater number along certain portions of tiie rays ; Avhile the median 

 and lateral plates have increased so much in size that the terminal plate 

 has lost entirely the preponderance whicli it had in younger stages, and 

 the extremity of the arm actually assumes a rounded outline. The dorsal 

 tubes (d'") are found numerous on both sides of tlie median arm-plate, 

 and along the edge of the oral lateral plates (d"), diminishing somewhat 

 in size as 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 clew 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 pedicellariae 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 pedicellariae [p, ;/'), found at their base. It 

 was impossible in these young Starfishes to discover the place of the 

 madreporic bod\^ 



[Professor E. Perrier has published a very elaborate and beautifully 

 illustrated memoir on the Pedicellarioe of Echinoderms in the Annales des 

 Sciences Naturelles. For the discussion of the nature of Pedicellariae see 

 an account in the Revision of the Echini, Part IV., by A. Agassiz, and an 

 article in the American Naturalist, Vol. VII.] 



From the oral side these Starfishes (PI. VIII. Fig. 9) exhibit scarcely 

 any difference from those of the stage last described, with the exception 

 of the somewhat more crowded ambulacra. There is a row of median 

 ambulacral spines (ii), 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 absence of a 

 well-defined interambulacral system. The young Starfish is still emi- 

 nently 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 Asteracanthion, that his Pedicellaster will turn out 



