132 Messrs. Koren and Danielssen on the Development 



on the parasites of the marine Molhisca. The locality beaten 

 by the waves was by no means favourable, and I was only once 

 able to find in the Conus Mediterraneus a fine flask- shaped Redia 

 with a long, but usually retracted neck, a very large pharyngeal 

 bulb, a short intestine, and a well-developed vascular system. 

 I am compelled to confine myself to this mere indication, 

 because the offspring which it contained was only in the state 

 of germs. 



XIV. — Observations on the Development of the Star-fishes. 

 By J. Koren and D. C. Danielssen*. 



Sars was the first to make known to us the history of the 

 development of the Star-fishes, in Wiegmann's Archiv, x. p. 169. 

 Subsequently, in the ' Fauna Littoralis Norvegise,' p. 47, he fur- 

 nished complete observations upon the Echinaster sanguinolentus, 

 Miiller, and the Asteracanthion Mulleri, Sars. Here he described 

 minutely the external changes passed through by the embryo 

 until it acquires the radiate form. Unfortunately, he did not 

 succeed in explaining the internal organization. The Star-fishes 

 observed by Sars belong to the section in which the development 

 takes place without any peculiar larval apparatus. 



A short time afterwards, Desorf published the history of the 

 development of a Star-fish, which took place nearly in the same 

 way as that described by Sars, except that in place of four 

 clavate prehensile arms, there was only one, which was always 

 ventral, and placed near the middle of the Star-fish. With 

 regard to this organ, Sars and Desor are at variance. Sars sup- 

 posed that the four prehensile arms left a cicatrix, which became 

 the madreporic plate. Desor, on the contrary, regarded the 

 claviform prehensile arm as a vitellary sac, which diminished in 

 proportion as the little Star-fish increased in size, until at last it 

 disappeared altogether. 



Subsequently, Agassiz J published his observations, which for 

 the most part agree with those of Desor, although he does not 

 say that the claviform stem becomes an appendage of the di- 

 gestive organs. Agassiz says that he has seen the contents of 

 the stem turn upon themselves. W. Busch§ observed and 



* Translated from the Fauna Littoralis Norvegise, Part ii. p. 55. By 

 W. S. Dallas, F.L.S. 



t Proc. Boston Soc. Nat. Hist. Feb. 15, 1848 ; Miiller's Archiv, 1849, 

 p. 79. 



t American Traveller, Dec. 22, 1848; Miiller's Archiv, 1851, p. 122. 



§ Beobachtungen iiber Anatomic und Entwickelung einiger wirbellosen 

 Seethiere, p. 77. Berlin, 1851. 



