ABSTRACT
The nettling response of coelenterate nematocysts (nettling capsules or cnidae), as it occurs in a natural manner, often involves the capsules themselves being cast off from the animal’s body surface. The latter event might be taken as a simple mechanical effect of the tension which is exerted upon the stinging thread when this becomes attached to the struggling victim. Parker & van Alstyne (1932), however, tend to see in it an active participation of the organism. They showed that a solution of ether in sea water caused the cnidae to go out of the acontia of Metridium with their threads still undischarged, and suggested it to be an agent imitating that ‘final step in the nettling operation’.
The acontium of Diadumene luciae contains also far smaller ‘basitrichous isorhizas ‘(see Hand, 1955), which were found to show behaviour different from that of the mastigophores either as to extrusion or discharge; they were not extruded in a salt-free medium.
Published values of Dittmar’s standard sea water for Cl− and Br− were, on re-calculation, 0·563 M and 0·00085 M, respectively. Added together, they correspond to a chlonmetric strength of M/I-776. Sea water which was used in the present experiments has actually given the value of M/1·793 on chlorimetry. Hence, M/1·8 instead of M/2-O may have been the exact molarity of NaCl equivalent to sea water, provided one may assume the applicability of simple summation of effects between different anionic components.
He mentions as such K-rich (M/8-M/4) sea water, as well as ether, triacetin (a %) and quinine (0·1 %), each dissolved in sea water.
