38 ACALEPHA. 



that of stunning and arresting active prey, which 

 is then passed to the mouth and swallowed. The 

 capsules are often crowded together at intervals, 

 forming thickened rings around the tentacles, and 

 their power is so great as to render some species 

 truly formidable to man himself. The great Cya- 

 ncea capillata of our own seas, for example, is a 

 species that stings most severely. 



Around the margin also are placed the organs of 

 sense. In one group called "Naked-eyed," there 

 are bulbs or swellings at the bases of the tentacles, 

 containing masses of coloured grains (pigment 

 cells) usually bright red or black, which are 

 believed to be rudimentary eyes. But in another 

 group, the one called " Covered- eyed," the organs 

 of vision are more complex, consisting of little 

 columns inclosing a vast number of six-sided prisms 

 of transparent substance, and protected by over- 

 hanging folds of membrane. In the former group 

 there are also on the margin little globules of trans- 

 parent membrane, inclosing one or more vibrating 

 bodies, and believed to be organs of hearing. 



The beauty of these creatures is very great ; 

 their elegant forms, their crystalline transparency, 

 their beautiful tints, their brilliant eye-specks, the 

 grace of their muslin-like frills and furbelows, their 

 pulsatory movements, all combine to make them, 

 especially the smaller species, most attractive sub- 

 jects of observation. Many of them exhibit in the 

 dark the curious and interesting phenomenon of 

 self-luminosity. On being touched or otherwise 

 irritated, they suddenly become illuminated, the 

 light appearing in rings or circles of luminous 

 points, which alternately flash and die, like gas-jets 

 on a festive gala-night. 



