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larva with its bilateral ciliated band passes into the radial type, as 

 in the larva of Comatula: it has a cylindrical form with five trans- 

 verse bands of cilia. From this pupa-state the Echinoderm is 

 developed without the rejection of any part of the pupa. It is either 

 formed upon a part of the pupa, and the rest is absorbed by it 

 ( Tonnaria of certain Asterice) , or the entire pupa is simultaneously 

 metamorphosed into the Echinoderm (Holothurice) . In both these 

 cases, but especially the first, the axis of the Echinoderm does not 

 coincide with the axis of the larva, but crosses it at a large angle. 

 Caecal processes are formed round the stomach of the larva in con- 

 nexion with the vesicle of its aquiferous system : they are the 

 rudiments of the water-canal around the mouth of the Echinoderm 

 and of the vessels which proceed to the tentacles and feet. Where 

 the afferent water-tube meets the surface of the Echinoderm the 

 madrepore-plate is formed, and the portion of the tube within the 

 body of the Echinoderm becomes its stone- or lime-canal. In Ophiurce 

 the madrepore-plate has been discovered by MUELLER*, its pores do 

 not open externally being covered by a plate of the inferior surface 

 of the disc. In Holothurice it is within the abdominal cavity, in 

 Asterice on the dorsal surface, in Echini it coincides with one of the 

 genital plates. In all these cases a tube, whether it be hardened 

 by carbonate of lime (stone-canal) or not, runs from the madre- 

 pore-sac or plate to the circular aquiferous canal surrounding the 

 oesophagus.] 



The power of reproduction in Echinoderms is very great. Star- 

 fishes are frequently seen with one or more small arms or rays, that 

 have been formed anew in consequence of the loss of the parts. 

 GUETTAKD and BERNARD DE JIJSSIEU confirmed the reproduction 

 by many experiments 3 . In Holothurice even viscera may be lost 

 and formed anew; and some species are propagated by spontaneous 

 division 4 . 



1 MUELLEB Archiv. 1850, p. 121. 



2 Comp. MUELLER Die larven u. metamorphos. der Ophiuren u. Seeiyel. Berlin, 1848, 

 1849 an( ^ I 85 2 ' MUELLER Uber die larven u. metamorph. der Ifolothurien u. Astcrien, 

 Berlin, 1850. MUELLER Ueber den allgemeinen Plan in der Entwidceluny der Echinoder- 

 men. Berlin, 1853. 



3 REAUMUR Mem. pour servir a PHist. des Ins. vi. Preface, pp. 6r, 62. 



4 According to the observations of SIR J. GRAHAM DALZELL, quoted by FORBES, 

 Hist, of British Star-fishes, pp. 199, 200. 



