ACALEPH.E. 197 



When the Medusae travel, their convex part is always kept in 

 advance, and slightly oblique. If they are touched while swimming, 

 even lightly,, they contract their tentacula, fold up their umbrella, 

 and sink into the sea. Like Ehrenberg, M. Kolliker thought he dis- 

 covered visual and auditory organs in an Oceania, and Gegenbauer 

 thought he detected them in other genera, such as Rhizostoma and 

 Pelagia. The eyes are said to consist of certain small, hemispherical, 

 cellulose, coloured masses, in which are sunk small crystalline globules, 

 the free parts of which are perfectly naked. The supposed auditory 

 apparatus is seated close to these organs ; they are small vesicles 

 filled with liquid ; the eyes having neither pupil nor cornea, and the 

 ears without opening or arch. 



But it is in their reproduction that these evanescent beings present 

 the most marvellous phenomena. At one period of the year the 

 Medusae are charged with numbers of very minute eggs, of the most 

 lively colours, which are suspended in large festoons from their 

 floating bodies. In some cases these eggs develop themselves grafted 

 to their bodies, and are only detached at maturity. In other cases 

 the larvae produced bear no resemblance to the mother ; they are 

 elongated and vermiform, broad at their extremity ; we speak of the 

 microscopic leeches, which have vibrating cilia, scarcely perceptible, by 

 which they execute the most lively motions. At the end of a certain 

 time they are transformed into polyps, and furnished with eight 

 tentacula. This preparatory sort of animal seems to possess the faculty 

 of reproduction by means of certain buds or tubercles which develop 

 themselves on the surface of the body, and also by filaments which 

 start up here and there, so that a single individual originates a 

 numerous colony. This polyp is subjected to a transformation still 

 more remarkable ; its structure becomes complex, its body articulate, 

 and it seems to be composed of a dozen disks piled one upon the 

 other, like the jars of a voltaic pile ; the upper disk is convex, and is 

 separated from the colony after a convulsive effort ; it becomes free, 

 and an excessively small, star-like Medusa is the result ; every disk, 

 that is, every individual, is isolated one after the other in the same 

 manner. 



Thus of the sexual zoophytes which propagate their kind according 

 to the usual laws ; but others engender young which have no resem- 

 blance to the parent zoophyte at all : in this respect they are neuter, 



