DIVERSITY OF FORM. 33 



The organs concerned in inflicting this " prickly torture," are 

 threads of extreme tenuity, which are coiled up iu minute 

 capsules that occur in great abundance in the tentacles of the 

 Jelly-fish and in various parts of the body. The slightest pres- 

 sure causes the capsules to burst, when the liberated threads 

 shoot out with amazing rapidity and force, piercing the object 

 of attack, and conveying into the wounds they inflict some 

 subtle poisonous fluid with which the animals are supposed to be 

 armed. 



Most of the Jelly-fish which commonly frequent our own 

 coasts belong to the Medusce, which may be regarded as the 

 most typical division of the class. The animals belonging to it 

 are distinguished, for the most part, by the possession of an. 

 ambrella-shaped disc, by the alternate expansion and contrac- 

 cion of which they propel themselves through the water. From 

 the trivial circumstance that these movements of the disc have 

 a resemblance to the heaving of the chest in respiration, the 

 Medusa} have received the name of pulmonigrades, or lung- 

 movers. It is only in calm weather, however, that the feeble 

 strokes of the disc avail the Medusa? for the purpose of locomo- 

 tion : during the prevalence of high winds the animals either 

 descend to the tranquil depths, or, remaining near the surface, 

 are driven helplessly along, and not unfrequently are cast in 

 myriads upon the shore. 



A considerable diversity of form obtains amongst the Medusse, 

 notwithstanding their general points of resemblance. Mr. Gosse 

 compares them to the glass-shades of the gas-lights which show 

 so conspicuously in the shop windows on a winter evening ; 

 and, so far as it goes, the comparison is a good one, only it does 

 not convey an adequate idea of the great variety of shapes which 

 the Medusae assume. In some species the disc is only slightly 

 convex, and the animal, when seen floating calmly in the water, 

 has the appearance of a mere circular patch of jelly. In others, 

 again, the disc rises proudly in the shape of a beautiful translu- 

 cent dome, or assumes something approaching to the elegant 

 pointed form of the Turkish minaret, while various leaf-like 

 processes hang from the interior, and long thread-like filaments 

 stream from numerous points around the circumference. Many 

 of the smaller species are like thimbles, both in size and form ; 

 while others have the appearance of beads or berries, except 



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