THREAD-CAPSULES. 123 



tliat in its substance were imbedded a great number of 

 filiferous capsules, exactly resembling in essential 

 points, those of certain Medusae. 



The capsules are transparent and colourless, in 

 shape a long oval from ^ to ^^ inch in length, and 

 are seen to contain a thread closely coiled. When 

 the pressure reaches a certain point, the capsule 

 shoots forth from one end the elastic thread, which 

 in a moment starts out like a spring to a length thirty 

 times as great as that of the capsule : sometimes in a 

 straight line, sometimes in a serpentine or (as 1 

 rather believe) a spiral form. The capsules do not 

 hurst, yet at the instant of the propulsion of their 

 filament there is a distinct crack heard. 



I now cut off carefully, with fine-pointed scissors, 

 two or three tentacles from one fully expanded, and 

 submitted them to the same scrutiny. The rounded 

 head of the tentacle appeared rather rough or hairy 

 at first, but as pressure began to flatten it, filiferous 

 capsules were seen to be protruding from the outline, 

 which increased in number as the pressure proceeded, 

 until an amazing multitude appeared, and the whole 

 substance of the tentacle-head was seen to be literally 

 composed of these capsules, as thick as spiculse in any 

 sponge, with only a slight quantity of gelatinous mat- 

 ter to hold them together. To see these thousands of 

 little vesicles discharging their missiles in rapid 

 succession, like the flights of arrows in ancient battles, 

 w^as an astonishing sight. When the propulsion 

 could be distinctly followed by the eye there was always 

 seen a little zigzag line on each side of the thread 

 reaching to a considerable distance from the base, 



