136 JOURNAL OF THE [Julv, 



Other the absence of any explanation leaves his intention entirely 

 to the choice of the reader. In fact Prof. Huxley is the only 

 authority with whom I am acquainted whose utterances on this 

 subject are at all open to doubt. All the rest are of opinion 

 that the ecthorasum is turned completely inside out, though the 

 word evagination, which some of them use to designate the 

 operation, is defined by Worcester as "the act of unsheathing," 

 which well describes a drawing or pushing of the thread through 

 the sheath or neck which forms at the anterior end of the cap- 

 sule just before the movement of the thread begins. 



If it were not for the drawings which Prof. Huxley gives us 

 in close proximity to tlie sentence I have taken from his book, 

 I should not hesitate to think that he accepted the prevailing 

 idea, derived from Gosse's observations and descriptions, — par- 

 ticularly in view of his explicit declaration that the filament is 

 hollow. But Huxley's pictures of nematocysts with extended 

 neck and thread are not the traditional representations, and do 

 not seem to be consistent with the traditional theory of intro- 

 reversion. On the contrary, they appear to illustrate, with re- 

 gard to one of the Hydrozoa, a process of direct propulsion 

 which, I believe, is also demonstrated, in respect to one of the 

 Actinozoa, by the specimen which we have under the microscope 

 this evening. 



The internal capsule, which is visible in many of the unex- 

 ploded nematocysts of the smaller forms, disappears when the 

 thread is emitted, and I think it is turned inside out and then 

 forms the neck of the bottle-shaped cell, and that through it the 

 thread is shot. I feel confident that the eversion of the neck 

 is all the turning inside out that takes place in any of the thread- 

 cells of Isophyllia, and that the thread itself goes straight for- 

 ward. It is probable that, if one could see the movement of the 

 thread immediately after the eversion of the neck, it would be 

 correctly described in the words used by Mr. Gosse when he 

 said he had "seen the unevolved portion of the ccthonvum run- 

 ning out through the centre of the evolved ventricose portion;" 

 for of course, at that stage of the operation, he could not tell 

 whether there was any connection or not between the enveloping 

 neck and the enclosed swiftly gliding thread. Mr. Gosse is an 

 accurate observer, and I do not question his statements of what 



