314 
Z. ASCIDIOIDA. 
Alcyonella. 
ovary. If a recently dead specimen in which the papillae are reduced 
to the state above described, be examined with the lens, a succession 
of air-bubbles are seen frequently escaping* from the horny tubes. 
By the successive formation and ascent of these bubbles, the ova 
which at this period are loose and floating in the tubes, are gradually 
elevated and conveyed to the exterior. In November, many of the 
specimens were seen with air-bubbles and ova successively escaping, 
and the external surface was covered by ova thus conveyed to the ex- 
terior. Those specimens which were black and putrid, and appeared 
to have been dead some time, exhibited the horny tubes nearly de- 
void of ova. After a time the horny basis itself becomes softened, 
and appears to undergo decomposition. During the following spring, 
according to the evidence of Vaucherand Raspail, the horny envelope 
of each ovum separates into two lateral halves adhering on one side 
as by a hinge. From these valves a small gelatinous tubercle pro- 
jects, which soon expands into a distinct polype, and gradually be- 
comes elongated into a tubular form. From the sides of this tubu- 
lar polype, small gelatinous buds soon appear, and these again be- 
come developed into distinct polypes ; the tubular parietes gradually 
become consolidated, and form the horny basis of the mature Al- 
cyonella.” 
Fig. 48. 
