i6 CORALS AND CORAL ISLANDS. 



" It has long been known, that a very slight contact with the 

 tentacles of a polyp is sufficient to produce, in any minute 

 animal so touched, torpor and speedy death. Since the dis- 

 covery of these c/iida; (lasso-cells) the fatal power has been 

 supposed to be lodged in them. Baker, a century ago, in 

 speaking of the Hydra, suggested that ' there must be some- 

 thing eminently poisonous in its grasp ; ' and this suspicion 

 received confirmation from the circumstance that the Entomos- 

 traca which are etiveloped in a shelly covej'lng frequently escape 

 unhurt after having been seized. The stinging power possessed 

 by many Medusae, which is sufficiently intense to be formid- 

 able even to man, has been reasonably attributed to the same 

 organs, which the microscope shows to be accumulated by 

 miUions in their tissues. 



" Though I cannot reduce this presumption to actual cer- 

 tainty, I have made some experiments, which leave no reason- 

 able doubt on the subject. First — I have proved that the 

 edhorceum (tubular thread of the lasso-cell) when shot out, has 

 the power of penetrating, and does actually penetrate, the 

 tissues of even higher animals. Several years ago, I was 

 examining one of the purple acontia of Adamsia palliata ; no 

 pressure had been used, but a considerable number of cnidcc 

 had been spontaneously dislodged. It happened that I had 

 just before been looking at the sucker-foot of an Asterina, 

 which remained still attached to the glass of the aquatic box, 

 by means of its terminal disk. The cilia of the acofitiiim had, 

 in their rowing action, brought it into contact with the sucker, 

 round which it then continued slowly to revolve. The result 

 I presently discovered to be, that a considerable number of 

 cnidce. had shot their ecthorcea into the flesh of the sucking-disk 

 of the Echinoderm, and were seen sticking all round its edge, 

 the wires (lassos) being imbedded in its substance even up to 

 the very capsules, like so many pins stuck around a toilet pin- 

 cushion. 



'' To test this power of penetration still farther, as well as to 

 try whether it is brought into exercise on the contact of a 

 foreign body with the living Anemone, I instituted the follow- 



