THE ANNALS 



AND 



MAGAZINE OF NATURAL HISTORY, 



SUPPLEMENT TO VOL. XIX. JUNE 1847. 



XLV.— »0w the Larval State and Metamorphosis of the Ophiuridse 

 and Echinidse. By Prof. J. Muller*. 



[With a Plate.] 



I HAD occasion last year to describe some animal forms observed 

 near Heligoland, among which was one peculiarly remarkable from 

 its form and skeleton, to which I gave the name of Pluteus para- 

 doxus. During the present year I have been able to extend my 

 observations and to study the further development and metamor- 

 phosis of this remarkable animal, which have proved highly inter- 

 esting. In fact, an Ophiura is developed from it ; Pluteus para- 

 doxus is consequently the larva of an Ophiura. 



The first observations instituted on the development of an 

 Echinoderm were those of M. Sars on Echinaster sanguinolentus 

 {Echinaster Sarsii, MiilL, Trosch.) and Asteracanthion MUlleri, 

 Sars. This naturalist, to whom we are already indebted for the 

 discovery of many important facts on the changes in form of the 

 lower animals during their development, has also observed, that 

 the young Asteria have no similarity to their later forms. The 

 larva of Echinaster, when it escapes from the ovum, is of an oval 

 form, without any external organs, and by means of innumerable 

 cilia which cover the body swims about free in the water just as 

 the Infusoria, or the Medusce, Coryne and Alcyone in their young 

 state do. In a few days organs grow out at that extremity of 

 the body which, when they swim, is seen to be the anterior ; 

 these serve for attachment. They consist of four bulbous tu- 

 bercles with a smaller one in the centre. By the aid of these 

 organs the young one fixes itself firmly to the marsupial cavity of 

 the mother. These tubercles disappear when the body of the 

 animal is developed into the radiate form. M. Sars has not given 

 any illustration of the internal structure of these young Echino- 

 dermata or larvae, which is sufficiently explained by their being 

 perfectly opake. 



The larvse of the Echinodermata, which form the subject of the 

 present notice, are so transparent, that they admitted of a mi- 

 croscopic analysis with a magnifying power of 250 diameters. 



* Translated by Dr. Griffith from the Berichte der Berliner Akademie for 

 Oct. 29, 1846. 



Ann. ^ Mag. N. Hist. Vol. xix. Suppl. 31 



