194* JELLY-FISH, STAR-FISH, AND SEA-URCHINS. 



seconds, and continues for a variable number of 

 seconds. It generally begins with powerful con- 

 tractions, of a less shivering character than those 

 which are produced by acids, and therefore still 

 more closely resembling the normal swimming 

 motions of the unmutilated animal. Sometimes, 

 however, the first manifestation of the artificial 

 rhythm is in the form of a few gentle rhythmic 

 contractions, to be followed by a few seconds of 

 quiescence, and then by the commencement of the 

 sustained bout of strong contractions. In either 

 case, when the bout of strong contractions sets in, 

 the rate of the rhythm becomes progressively and 

 rapidly increased, until it runs up into incipient 

 tetanus. The rate of the rhythm still quickening, 

 the tetanus rapidly becomes more and more pro- 

 nounced, till at last the bell becomes quiescent in 

 tonic spasm.* 



If the bell is still left in the glycerine solution 

 nothing further happens; the tissues die in this 

 condition of strong systole. But if the bell be 

 transferred to normal sea-water immediately after, 

 or, still better, slightly before the tonic spasm has 

 become complete, an interesting series of pheno- 

 mena is presented. The spasm persists for a long 



* Sometimes, however, the order of events is slightly different, 

 the advent of the spasm being more sudden, and followed by a 

 mitigation of its severity, the bell then exhibiting what is more 

 usually the first phase of the series, namely, the occurrence of 

 the locomotor-like contractions. Occasionally, also, rhythmical 

 shivenng contractions may be seen superimposed on the general 

 tonic contraction, either in a part or over the whole of the con- 

 tractile tissues. 



