I/O THE OCEAN WORLD. 



spheres. These eggs are transformed into oval larvse, covered with 

 vibratile cilia, having a slight depression in front. They swim about 

 for a short time with great activity, much like some of the Infusoria, 

 which they strikingly resemble in other respects. 



At the end of forty-eight hours their movements decrease. Aided 

 by the depression already noted, the larval form attaches itself to 

 some solid body, fixing itself to it at this stage by the presence of a 

 thick mucous matter. A change of form soon takes place : it becomes 

 elongated; its pedicle is contracted, and its free extremity swells into 

 a club-like shape. An opening soon presents itself in the centre of 

 this extremity, through which an internal cavity appears. Four little 

 protuberances have now appeared on the edge, which are in time 

 elongated in the manner of arms. Others soon follow : these are the 

 tentacles of a polyp : the young infusorian has become a polyp ! 



The polyp increases by buds and shoots, just like a strawberry 

 plant, which throws out its slender stems in all directions, covering 

 all the neighbouring ground. 



The young Medusa lives some time under this form. Then one 

 of the polyps becomes ^ enlarged and its form cylindrical. This 

 cylinder is divided into 'from ten to fourteen superimposed rings. 

 These rings, at first smooth, form themselves into festoons, and 

 separate into bifurcated thongs ; the intermediate lines become 

 channeled. The animal now resembles a pile of plates, cut round 

 the edges. In a short time each ring is slightly raised at the free 

 edge of its fringe : this then becomes contractile. The rings are 

 individualised. Finally, these disc-shaped creatures isolate them- 

 selves. When detached, they begin to swim : from that time they 

 have only to perfect and modify their form. From being flat, they 

 become concave on the one side and convex on the other. The 

 digestive cavity- -the gastro-vascular canals become more decided ; 

 the mouth opens on the concave surface; the tentacles are elongated; 

 the floating marginal cirri become more and more numerous ; and 

 now, after all these metamorphoses, the Medusa appears ; it perfectly 

 resembles, not the parent form, but that from which its parent 

 form originally sprung. 



