REPRODUCTION. 



Ill 



series of transverse arm illations or grooves (fig. 32, c). These 

 grooves go on deepening, and the segments which they mark 

 off become deeply lobed and incised at their margins, till 

 the whole organism assumes the aspect of a pile of saucers 

 arranged one upon another with their concave surfaces up- 

 wards. A new set of tentacles is developed near the base of 

 the organism, and all the segments above this point gradu- 

 ally fall off, and swim away to lead a free life. These libe- 

 rated segments of the little Hydra-tuba (it is about half an 

 inch in height) now lead an independent existence, and 

 were originally described by naturalists as distinct animals 

 (fig. 33). They are provided with a swimming-bell or "urn- 



Fig- 33- Hidden-eyed Medusae. Generative zo5id of one of the Litcernarida 

 (Chrysaora hysoscella). After Gosse. 



brella," by the contractions of which they are propelled 

 through the water. From the centre of the umbrella is sus- 

 pended a modified polypite with lobed and scalloped lips ; 



