44 FEBRUARY. 



foot, is observed to develop itself a little behind them, 

 on the medial line ; a shell closely investing the infe- 

 rior portion of the embryo, the lobes and rudimentary 

 foot being uppermost. The shell rapidly increases, and 

 assumes a nautiloid form ; afterwards the foot displays, 

 attached to its posterior surface, a circular operculum, 

 which is opposed to the mouth of the shell. The lobes 

 now expand into two large, flattened, ovate appendages, 

 with very long vibratile cilia around the margins ; and 

 the larvae are at length mature. The whole mass of 

 spawn now presents the utmost animation. Hundreds 

 of these busy atoms are seen, each within its trans- 

 parent, membranous cell, rotating with great agility 

 and ceaseless perseverance, the cilia all the while vigor- 

 ously vibrating on the margins of the outstretched 

 lobes. The membranous chorion [or transparent egg- 

 shell], which by this time has become enlarged, ulti- 

 mately gives way, no longer able to resist the perpetual 

 struggle within ; and the liberated larva, wending its 

 way through the shattered shreds of the general envelope, 

 boldly trusts itself to the open trackless water, where, 

 doubtless, thousands and tens of thousands perish ere 

 they find a fitting resting-place, some being swept away 

 by resistless currents, others falling a prey to ever- 

 watchful and innumerable enemies. 

 " When the larva is at rest, the oral lobes are pulled 



