Embryology o/Ophiocoma echinata, Agassiz. 



459 



by Metschnikoff and in starfish larvae by Brooks and Field, I 

 find that soon after their formation the two anterior pouches 

 botli communicate with the exterior through pore-canals 

 which open on the dorsal surface of the larva. 



At about the time of the formation of the pore-canals or a 



r a>p~ 



„.* up 



little before, the larval mouth breaks through on the ventral 

 surface and there is formed the perfect bilaterally symmetrical 

 larva shown in fig. 3, which is the optical section of a larva 



-}-pc 



tying on its dorsal surface, the outlines having been made 

 with a camera lucida. 



The pore-canals are not, as Bury describes, intracellular 



