34 EMBRYOLOGY OF THE STARFISH. Part I. 



after it. The water-pore remains in the position in which it was at first, in the 

 angle of the arm (/{'), which opens the pentagon, and is encased in a stronger 

 deposit of limestone. 



Resorption of the Brachiolaria. — While the Starfish is growing upon the outer 

 surfaces of the two opposite water-tubes, and is gradually becoming a part of the 

 Brachiolaria, no changes take place in the external appearance of the larvse (PI. 

 IV. Figs. 1, 2 ; PI. VII. Fig. 8). But when the Starfish has become so far ad- 

 vanced as to occupy a very prominent position at the anal extremity of the larva 

 (PI. IV. Fig. 4 ; PI. VII. Fig. 8), the complicated appendages designated as arms, 

 which have served for the development and for the locomotion of the Starfish, are 

 resorbed by the little Echinoderm. 



We now come to a most interesting period in the history of our Starfish. The 

 larvse, very active up to this time, grow sluggish ; the body, which, with the 

 exception of the anal portion, is, in the early stages, perfectly transparent and clear, 

 becomes cloudy and opaque. Changes are first visible in the side arms (PL IV 

 Figs. 7, 8, 9) ;. they contract, and apparently divide into many large cells. Next in 

 turn the anal ventral arms, and, lastly, the dorsal arms, contract in the same manner. 

 This contraction of the arms is accompanied by a corresponding shrinking of the 

 anal part of the larva, beyond the mouth (PI. IV. Fig. 9), so rapid that in a few 

 hours the anal arms have shrunk to quite a small compass (PL IV. Fig. 9) ; the 

 oral dorsal arms, and the oral ventral arms contract in their turn, until there 

 remains nothing but the brachiolar arms, brought close to the Starfish by the 

 shrinking of the mass of the body (PL IV. Fig. 8). They soon follow the rest, 

 and we can actually see the gradual disappearance of this complicated fabric. It 

 has served its purpose of developing and feeding the young Starfish, which has 

 now reached a state when, in a few hours, it will move about independently, having 

 resorbed, for what purpose is not known, the whole of the framework. Mot a 

 single part is dropped off, the whole of the larva passes Mo the Starfish, and, before 

 twelve hours have elapsed from the commencement of the first sign of contraction 

 of the anal tentacles, nothing is to be seen of the larval appendages, except a few 

 indistinct swellings on the actinal side of the little Starfish (PL VI. Fig. 1). 



The Starfish after the Resorption of the Bipinnaria. — The process of resorption, 

 which I have frequently had the opportunity to examine and trace in all its stages, 

 leaves no doubt, at least in this case, that the young Starfish does not separate 

 from the Brachiolaria. We cannot, therefore, consider the Starfish and the frame- 

 work (the Brachiolaria) as two individuals, leading a separate existence at different 

 stages of growth, but must regard them both as one and the same thing. This 

 is in direct contradiction to the statements of Miiller, and of Koren and Danielssen, 

 with regard to the Echinoderm, the development of which they have had occasion 



