I'ROCEEDINGS OF THE NATIOXAL MUSEUM. 735 



the last ill liaving the greater portion of its basal i)ait covered by long 

 slender spines. In the discharged or evaginated condition, tlie tliread 

 is at least partially tilled by the lluid contents of tlie capsnle. 



In order to cause the iK'niafoci/st to be discharged, a proper stimulus — 

 a minute crustacean, or worm, or an enemy — must come into contact 

 witli the ciiidocil, ibr it is the sensory part of the nettling organ. Tlie 

 stimulus at one cnidocil may be distributed by nerve connections to 

 the surrounding nettling organs, thus inducing explosions en masse. 

 Next the cell-body and stalk contract, and this double pressure on the 

 nematocyst, is transmitted by its fluid contents to all parts of the 

 thread within, and it begins to be evaginated from its basal part out- 

 ward to its end, with explosive rapidity.' The thread newly shot 

 out unites the two very efficient conditions, namely, a large adhesive 

 surface enhanced by very minute barbs, and by a sticky substance 

 which also acts as a poison.'^ 



The nettling poison has never been chemically analyzed, but its nature 

 has rather been inferred from its effect on other animals. It was for- 

 merly supposed by many to be somewhat similar to formic acid. The 

 small animals that are caught by a Cuidarian as prey make a few con- 

 vulsive movements and then are apjiarently dead and are ingested by 

 their captor. Anyone may experience the effect of the fluid in a more 

 marked degree than on the hands, if he will touch his tongue to the 

 t -ntacles of a sea anemone. It is not unlike the sensation perceived on 

 i( inching the tongue to a freshly cut root of Indian turnip (.L>-/.s;rn»rt. 

 tiiphyllum), and may last several hours or a day. Indeed, Professor 

 Leuckart records a case where a lead pencil which had some weeks pre- 

 viously been used in manipulating a sii)hono])hore, on being accidentally 

 touched to the tongue, caused this nettling.^ 



The above brief review of what is held at the present time on the 

 anatomy and i)liysio]ogy of the nettling organs also contains the 

 princi])al points of my recent ])aper on this subject.^ 



In that paper I reviewed the pertinent literature, and would refer 

 those who desire a fuller account to it. The x)receding has been given 

 to make clearer w^hat is to follow. For the same reason it may be well 

 to briefly give my results from alcoholic material on the development 

 and migration of nettling organs, as presented by the same paper. 



'In alcoholic material oue can occasionally cause the thread to be slowly everted 

 by continuous pressure on the cover glass. 



'-l>y all authors before lue, the noxious fluid was supposed to be contained in the 

 nematocyst. Their cliief argument for the belief that iluid flows from the capsule 

 IS, that the size of the capsule and thread is less after the discharge of tlie latter. 

 TLis does not hold when we remember that the volume of the lluid in the ca^isule 

 equals the volume of the cajtsule minus the volume of the contained thread. How 

 could this lluid then, after evagination of the thread, till both capsule and thread 

 as tensely as before? Besides this, all of the authors since Ma'bius, have left out of 

 account the substance (fluid) that fills the lumen of the in^'aginated thread. 



■^Zur naheren Kenutuiss der Siphonoi)horen von Nizza; Archiv f. Naturgesch., 1854. 



■"Archiv f. Naturgesch, Pt. 3, 1894. (one plate and one woodcut). 



