214 JELLY-FISH, STAR-FISH, AND SEA-URCHINS. 



agent is much the same as that of chloroform — the 

 description just given being quite as applicable to 

 the effects of tlie nitrite as to those of chloroform. 

 Before the loss of spontaneity supervenes, the rate 

 of the rh^^thm is increased, while the strength of 

 the pulsations is diminished. 



Tiaropsis diademata, from the fact of its present- 

 ing a very regular rhythm and being but of small 

 size, is a particularly suitable species upon which 

 to conduct many experiments relating to the effect 

 of poisons. On this species the nitrite in appro- 

 priate (i.e. in very small) doses first causes irregularity 

 and enfeeblement of the contractions, together with 

 quickening of the rhythm. After a short time, 

 a gradual cessation of the swimming motions be- 

 comes apparent — these motions dying out more 

 gradually, for example, than they do under the 

 influence of chloroform. Eventually each pulsation 

 is marked only by a slight contraction of the 

 muscular tissue in the immediate neighbourhood of 

 the margin. If the dose has been stronger, however, 

 well-marked spasmodic contractions come on and 

 obliterate such gradual working of the poison. In 

 all cases irritability of all parts of the animal 

 persists for a long time after entire cessation of 

 spontaneous movements — perhaps for three or four 

 minutes in not over-poisoned animals ; but eventu- 

 ally it too disappears. On being now transferred 

 to noi'inal sea- water, the process of recovery is 

 slower than it is after ansesthesiation by chloroform. 

 It is interesting, moreover, to observe, that just as 

 the power of co-ordination was the first thing to be 



