492 



THE MICROSCOPE. 



Fig. 23S —Jelly-fish. 



orders : A. stabiles (fixed), A. libera* (free), and A. hydro- 

 statica3 (hydrostatic). Cuvier classed them in two orders : 

 A. simplices and A. hydrostaticcs. They 

 are now, however, divided differently, 

 and arranged in groups according to the 

 peculiar mode by which they effect their 

 locomotion. A very interesting point of 

 connexion between this class and the 

 preceding is the interchange of form. 

 Some of the Zoophyta, as the Tubula- 

 riadtK and the Campanulariadce, give 

 birth to a progeny which are in every 

 respect Naked-eyed Medusae ; while, on 

 the other hand, the young of the Medusae 

 are in their earlier stages stationary 

 polypes. 



The Medusae spread on the surface of the water a beau- 

 ful jelly-like mass, in form resembling an umbrella ; and, 

 by a continual contraction and opening out of this, they 

 swim freely about (Plate IX. c, d, e, h). They are all 

 more or less phosphorescent. The Beroe, one of the family 

 Ctenophora, propel themselves with active ciliated arms. 

 The Physalidce have an organ common to fishes, — swim- 

 ming bladders, — by filling or emptying which they rise or 

 sink, and move along in their watery home. 



The Medusoid family, Lucemaridoe, has, from a mis- 

 taken view of its organization, been referred to the class 

 Actinozoa : Milne-Edwards has, however, placed it in a 

 sub-class, under the name of Podactinaria. In the 

 Lucernaridae the body is cup-shaped, about an inch in 

 height, terminating in a short foot-stalk. Round the 

 distal margin of the cup arise a number of short tentacles, 

 which are disposed in eight or nine turfts ; in Garduella 

 they form one continuous series. Their free extremities 

 appear sucker-like, and the whole organism is semi-trans- 

 parent, of a gelatinous consistence, and variously coloured. 

 The cup, viewed from above, presents in its centre a four- 

 lobed mouth, which is seen to form the free extremity of 

 a distinct polypite, occupying the axis of the entire 

 hydrosoma. Its gastric region exhibits a number of 

 tubular filaments, arranged in vertical rows dipping into 



