1 888.] NEW-YORK MICROSCOPICAL SOCIETY. 137 



he actually saw; but his interpretations of his observations are 

 not the only ones of which the facts are capable. 



After the thread is fully extended there remains at its base 

 a clear space, devoid of setae, about equal in length to the 

 shorter diameter of the cell, which is shown in Fig.V., and which 

 I believe to be the everted tube, or neck, above referred to. 

 This I take to indicate that the thread runs out to the extreme 

 point of the neck, where it is checked and held by some forma- 

 tion at the posterior end of the thread which acts as a wedge, 

 or jam, in the mouth of the tube, making an invisible joint and 

 producing an appearance as if the tube and the thread were 

 actually continuous. 



But the nematocyst pictured in Fig. III. affords us very strong 

 and unexpectedly striking proof that the thread is simply pushed 

 forward and not turned inside out, in the arrangement of the 

 setae upon the thread as seen both within and without the cap- 

 sule. We knovv that whatever slant the setae have upon a 

 wholly emitted thread is backwards, and we observe that the 

 setae upon the partly extended thread in Fig. III. have this same 

 inclination. We perceive, however, that there is no difference 

 in the direction of the setae upon that portion of the thread 

 which is still within the capsule, as there certainly would be if 

 the thread were being turned inside out. If a tube covered 

 with hairs were being thus treated, the hairs would not only have 

 opposite positions upon the two reversed sections of the tube, 

 but upon the everted portion they would be exterior and upon 

 the unturned part they would be interior to the tube. If, there 

 fore, the thread in Fig. III. were being ejected in the manner de- 

 scribed by Mr. Gosse, all the setje within the cell should be on 

 the inside of the thread, whereas they are clearly and unmis- 

 takably on the outside, like those already without the cell. 



Having made up our mind, then, that the thread is merely 

 driven through the neck of the bottle-like cell, it remains for us 

 to inquire what part the setae perform in this curious, but com- 

 paratively simple operation. This brings us to consider their 

 form and their mode of arrangement on the thread. Because 

 of the minuteness and delicacy of these really bristle-like appen- 

 dages, the best qualities of our modern objectives are required 

 to discern their character with any degree of certainty. It is 

 not strange, therefore, that at one time the threads of certain 



