6o 



ON THE ORIGIN AND 



[CHAP. 



of a Bipinnaria found by Miiller 1 near Marseilles. 

 a is the mouth, b the oesophagus, c the stomach, c 

 the intestine. Fig. 47 represents a somewhat older 

 specimen, in which the Starfish (/) is already begin- 

 ning to make its appearance. 



But while certain Starfishes thus go through meta- 

 morphoses similar in character, and not less remark- 

 able than those of sea-eggs, there are others as, for 



FIG. 45, Larva of Starfish (Bipinnaria), x 100 (after Miiller). 46, Larva of 

 Starfish (Bipinnaria), X 100, seen from the side , mouth ; b, oesopha- 

 gus ; c, stomach ; c', intestine. 47, Larva of another Bipinnaria, 

 showing the commencement of the Starfish g, canal of the ciliated sac : 

 *', rudiments of tentacles ; d, ciliated band. 



instance, the genus Asteracanthion in which deve- 

 lopment may be said to be direct the organs and 

 appendages special to the Pseudembryo being in 

 abeyance ; while in another genus, Pteraster, they 

 are reduced to a mere investing membrane. 2 



1 Loc. cit. Zweit. Abh. PI. i., figs. 8 and 9. 



2 Thomson, on the Embryology of the Echinodermata, Natural 

 History Review, 1863, p. 415. See also Agassiz, "Embryology of the 

 Starfish," p. 62. 



