300 THREAD-CAPSULES. 



eyes, very minute, colourless, and set around the 

 frontal margin of the anterior disk; the anus is 

 terminal. The ovary is large, and filled with a number 

 of clear, globular, highly refractile ova. Close-set 

 transverse annuli were conspicuous on the fore half of 

 the body. 



When the Medusa was subjected to pressure, I 

 observed several vesicles of exceedingly subtle mem- 

 brane, loosely wrinkled, containing a number (varying 

 from one or two to thirty) of clear oval bodies, about 

 jT^th inch in longest diameter. (See lig. 3). The 

 vesicles were placed at the end of a short canal, or 

 neck, or footstalk, of similar membrane, originating 

 from the marginal canal, and freely standing up on 

 the outside of the umbrella, as I believe. Each of 

 the oval granules had a body within it, which I at 

 first supposed a cell, but in one I distinctly saw that 

 it was composed of a number of oblique parallel lines 

 (See fig. 4). On pressure being increased, all the 

 oval capsules simultaneously shot forth, from one end, 

 a thread of great tenuity and of excessive length. I 

 could trace them to about fifty times the length of the 

 oval, and am not at all sure that I saw their extremity, 

 for with a power of 300 they became undistinguishable 

 farther. The thread, in an instant so brief as to be 

 inappreciable, assumed perfect straightness, (except a 

 slight curve in some cases), just as if composed of 

 some highly elastic substance, that had hitherto been 

 compressed But close examination showed an appear- 

 ance like that of a corrugated sheath enveloping it 

 for a considerable portion of its length, perhaps one 

 third, from the oval capsule (See fig. 5). 



