138 CLASS IV. 
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 Asteric), or the entire pupa is simultaneously 
metamorphosed into the Echinoderm (Holothuriw). 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. 
Cecal 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 Echimoderm 
and of the vessels which proceed to the tentacles and feet. Where 
the afferent water-tube meets the surface of the Kchimoderm the 
madrepore-plate is formed, and the portion of the tube within the 
body of the Echinoderm becomes its stone- or lime-canal. In Ophiure 
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 Holothurie it is within the abdominal cavity, in 
Asterice on the dorsal surface, in Echini it comcides 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. 
GueTrarD and BERNARD DE JUSSIEU confirmed the reproduction 
by many experiments’. In Holothurie even viscera may be lost 
and formed anew; and some species are propagated by spontaneous 
division‘. 
1 MuELLER Archiv. 1850, p. 121. 
2 Comp. MUELLER Die larven u. metamorphos, der Ophiuren u. Seeigel. Berlin, 1848, 
1849 and 1852. MvuELLER Uber die larven u. metamorph. der Holothurien u. Asterien, 
Berlin, 1850. MuELLer Veber den allgemeinen Plan in der Entwickelung der Echinoder- 
men. Berlin, 1853. 
3 ReaumuR Mem. pour servir a U Hist. des Ins. vt. Préface, pp. 61, 62. 
4 According to the observations of Sir J, GRAHAM DALZELL, quoted a FORBES, 
Hist. of British Star-fishes, pp. 199, 200. 
