21 
have been able to observe it, appears as a minute tubercle pro- 
jecting from the external walls of the cell, and filled with a 
granular parenchyma. We next find it hollowed out into a 
cavity which communicates with the interior of the parent cell. 
The tubercle, with its cavity, increases in size, and the gemma 
is now found to consist of an external envelope continuous with 
the external tunic of the parent cell, and ofa thick fleshy 
lining continuous with the internal tunic. This lining has nu- 
merous, large, round, nucleated cells distributed through its 
substance, and internally it presents a rough, uneven surface. 
The two tunics of the gemma are to become the external and 
internal tunics of the future cell. 
“¢ By this time the gemma has become considerably elon- 
gated, and has acquired a clavate form, and its cavity begins 
to be cut off from that of the parent cell, by the formation of 
a septum. We next perceive that a rounded mass has formed 
in the substance of the lining tunic, near the wide extremity of 
the gemma, and projects into the interior of the latter. In this 
mass we soon perceive a cavity surrounded by a slightly waved 
oval ring, which is afterwards to become the tentacular crown 
of the adult. The ring is at first quite simple, resembling a 
mere fold of thickish membrane, but in a short time it pre- 
sents all round a series of minute tubercles, the rudiments of 
the future tentacula. Delicate fibres may now be distinctly 
seen passing from the little mass, in which these appearances 
have been presenting themselves, to the walls of the cavity of 
the gemma; these fibres are the rudimental retractors of the 
alimentary canal. Circular fibres may also be now seen in the 
lining membrane of the gemma; these are chiefly collected 
near its proximal end, and are to become the parietal muscles 
of the adult. The tentacular sheath also may now be per- 
ceived extending from the base of the rudimental tentacula to 
the walls of the cavity in which the young polypide is sus- 
pended, and fibres which are to become the superior parieto- 
