M. Sars on the Development of Star-fislics. 237 



[Obs. — We have also seen, so far as we could prosecute the in- 

 quiry, that traces of the disappearance of the organs of attach- 

 ment are still left distinctly visible as two very small papilliform 

 projections, situated close together, and which appear to recede 

 more and more towards the dorsal surface. I am now, although 

 unable to demonstrate directly the fact, convinced, that what is 

 called the madreporoid plate in the adult Star-fishes is nothing 

 else than the remnant of the organs of attachment dwindled to 

 a single small tubercle. Joh. Miiller and Troschel, in alluding 

 to the problematical nature of this madreporoid plate, thus ex- 

 press their opinions concerning it : " At first sight it appears not 

 unnatural to compare this plate in the Asteriadce and Echini or 

 Sea-urchins with the knot of the Comatulce ; nor can the eccentric 

 position of the madreporoid plate be taken as any objection to 

 the analogy being drawn, for it is placed in the Clypeasters upon 

 the dorsal pole. Meanwhile, however, the constant occurrence of 

 more than a single madreporoid plate in some species of Star- 

 fish militates against the comparison, and its true signification 

 can be probably explained only by the study of its development. 

 According to the observations of Sars, the Asteriadce are freely 

 locomotive when young and not attached to rocks.'" 



If now my view of the madreporoid plate being a relic of 

 the organs of attachment be correct, we may very well compare 

 it with the knot of the Comatulce and the stem of other Crinoidea. 

 The authors already quoted, in objecting to this comparison con- 

 tained in my observations in Wiegmann's l Archiv * for 1837, ap- 

 pear to me to have contributed rather to substantiate than inva- 

 lidate the opinion. 



This view of mine relative to the nature of the madreporoid plate 

 must tend in an unexpected and remarkable manner to confirm 

 the ingenious theory advanced by Agassiz respecting the bilateral 

 type of the Echinodermata. For in addition, the organs of attach- 

 ment having been already proved to be placed in an interradial 

 interval, through which the long axis of the Star-fish passes, the 

 determination of the front and back of the animal given by the 

 same author becomes decisive, since that end of the body by which 

 the young Star-fish attaches itself must surely be taken for the 

 posterior. The Star-fish indeed, in its earliest state of adolescence, 

 swims with this end of the body directed forwards, on which ac- 

 count we might regard it as anterior, and this we have done pro- 

 visionally upon a former occasion ; but the analogy alone of othey 

 animals, such as the young of the Medusce, as I have described 

 them in their first or marsupial stage*, and of the compound 

 Ascidice observed by Milne Edwards f, lead us to the recognition 

 of the fact, that the end which during swimming was directed 



* Wiegmann's Archiv, 1841. 



t Observ. sur les Ascidies composees des cOtes de la Manche. 



