MEDUSIPAROUS REPRODUCTION. 131 



(PL II. fig. 5, v) may be detected amongst the usual 

 polyp-bearing cells, in the proportion of about one of 

 the former to thirty of the latter. Their position is 

 no farther peculiar than in being seated on the upper 

 side of the branches, and they are generally empty, 

 as if they had fulfilled the purpose for which they 

 were intended. When present, their number on a 

 branch sometimes amounts to eight or ten. 



These vesicles are of a grey, or a greenish colour. 

 When prolific, they contain twelve or more dull grey 

 corpuscula, each having a dark central nucleus, and 

 all appearing as if compressed together (PL II. fig. 5, a). 

 These little bodies, be it remarked, present no re- 

 semblance to the contents of the vesicles of the Ser- 

 tularia, which, as we have seen, make their escape 

 under the form of active Planula, but are evidently of 

 a very different nature, and well calculated to rivet 

 the attention of the most incurious who may be for- 

 tunate enough to procure them under circumstances 

 favourable for observing their strange history. 



When the contents of the reproductive vesicles of 

 the Campanularia approach maturity, some internal 

 movement becomes perceptible towards the upper part, 

 and at length the tips of the tentacula of an included 

 animal make their appearance, gradually protruding 

 from the summit of the vesicle, and these stretch- 

 ing further outwards, soon (PL II. fig. 5, b) begin to 

 contract convulsively, as if to free the body within. 

 After much apparent exertion this is at last accom- 

 plished, and we behold, to our astonishment, a Me- 

 dusa, which has escaped from its prison ! (PL II. 

 fig. 5, c,d). 



