THE MUSEUM. 



lOI 



botli external and internal, has the 

 power of absorbing oxygen; but it is 

 reasonable to conclude, that this takes 

 place most rapidly in the tentacles and 

 internal membranes where the struc- 

 ture fs most delicate. 



We usually notice, when trying to 

 remo\e one of these Actinias from its 

 rock, a large number of white thread 

 like organs emerging both from the 

 mouth and minute openings through 

 the sides of the body. These organs 

 appear to be for the defense of the 

 creature, since they are found to be 

 composed almost entirely of minute 

 poison-darts or lasso-cells, arranged 

 side by side, and having a deadly 

 stinging power when used against 

 small animals. In fact there are very 

 few of the predacious marine animals 

 even not excepting the voracious 

 fishes, that have the temerity to attack 

 one of the harmless looking Sea Anem- 

 ones; for though their darts may not 

 have sufficient power to kill a large 

 fish, they will, at least, penetrate the 

 thin membranes of the mouth and pro- 

 duce a severe stinging, like that of 

 nettles. And since these stinging 

 threads may be thrown out copiously, 

 and are several inches long, they are 

 very effectual organs of defense. The 

 inner ends of the threads are attached 

 the free edges of the radiating parti- 

 tions, and the free ends are thrown 

 out simply by the contractions of the 

 animal and conse(iuent expulsion of 

 the fluid contained in its body, which, 

 as it rushes out of the mouth and 

 through the loop holes of the sides, 

 carries with it the thaeads. When the 

 Actinia is again left in repose, it grad- 

 ually draws in its stinging threads. 

 The little poison darts, usually called 

 lasso-cells which cover both these 

 threads and the tentacles have a 

 wonderful structure for organs so mi- 

 nute. They consist of little vesicles 

 or cell filled with fluid, and have a 

 very long, extremely thin tube, coiled 

 up in the interior. This tube is con- 

 tinuously with one end of the vesicle 

 that contains it.so that when the vesi- 



cle is compressed or contracted the fluid 

 forces out the tabular dart by turning 

 it inside out. as one would turn the 

 finger of a glove. The slender tube, 

 when thrust out, is very long, slender 

 and pointed, and usually curiously and 

 wonderfully barbed. The nature of 

 the poison, so deadly to small ani- 

 mals, which these darts emit when 

 they penetrate the flesh, is still un- 

 known; but whatever its nature it 

 must be very powerful for the quantity 

 is necessarily excessively small. The 

 tentacles not only capture and kill the 

 prey by means of these organs, but by 

 means of the darts, that thus pene- 

 trate in large numbers, they hold it 

 firmly until conveyed from the tenta- 

 cles to the mouth. Among our native 

 Sea Anemones there are no species 

 that have darts powerful enough to 

 sting the hand, through some species 

 like the star anemone, will often ad- 

 here so firmly, if its tentacles be 

 touched by the finger that it may be 

 lifted from the water before it will 

 loosen its hold. This adherence is 

 doubtless due to the many lasso cells 

 ihat partially penetrate the epidermis 

 or outer layer of the skin, but have 

 not power to enter far enough to 

 reace the sensative portion. But the 

 common, large, red Jelly-fish (Cyaiica 

 arctica) has similar poison darts cover- 

 ing its long, floating, thread like tenta- 

 cles, which are powerful enough to 

 penetrate the human skin, and sting 

 far more powerfully than nettles. And 

 among the coral-roofs of Florida and 

 the West Indies there are corals {Mil- 

 Icpora) w-hich, unlike most corals, 

 have animals belonging to the same 

 class with the Jelly-fishes, on their 

 tentacles have poison darts, which ac- 

 cording to the observations of Prof. 

 Hartt, sting the parts of the hand 

 where the skin is most delicate very 

 severely. The same is true of some 

 other Hyiiroids, which do not form 

 coral but grow in mass- like tufts. It 

 is also said that some of the foreign 

 Sea Anemones have the same power 

 of stinging the hands, and especially 



