150 On the Locomotor System of Medusa. [Dec. 16, 



decided, both in the case of the naked- and of the covered-eyed MedusaB. 

 The first indications of approaching torpor are (a) decrease in the rate 

 of the pulsations and (b) diminution of their vigour. These indications 

 rapidly become more and more marked, so that shortly after they first 

 set in the period of diastole is very much prolonged and the systoles, 

 when they occur, are of the feeblest character. Eventually the pulsations 

 altogether cease ; and shortly after this stage of perfect quiescence has 

 been reached, the Medusa is quite insensible to all stimulation. Eecovery 

 in normal sea-water is very rapid, occupying only a few seconds in the 

 case of Sarsia ; but, like the reverse process of anaesthesiation, it is clearly 

 of a gradual nature. 



(b) Morphia is as decided in its action upon Medusae as is chloroform. 

 The processes of anaesthesiation and of subsequent recovery are very 

 similar to those just described, except that both processes occupy a some- 

 what longer time. 



(c) Strychnia exerts a very marked influence upon Medusas. Of the 

 species I have met with Cyancea ca/pillata is the most suitable for showing 

 the effects of this poison, from the fact that, in water kept at a constant 

 temperature, the normal pulsations of this animal are as regular as are 

 those of a heart. Shortly after a solution of strychnia has been added to 

 the water in which a specimen of C. capillata is contained, unmistakable 

 signs of irregularity in the pulsation of the animal supervene. This irre- 

 gularity then increases more and more, until at last it grows into well- 

 marked convulsions. The convulsions manifest themselves in the form 

 of extreme deviations from the rhythmical character of the normal con- 

 tractions, amounting, in fact, to nothing less than tonic spasms. It is 

 further of importance to remark that the convulsions are very plainly of 

 a paroxysmal nature — prolonged periods of uninterrupted convulsions 

 being every now and then relieved by shorter periods of repose, during 

 which the Medusa remains perfectly motionless in a fully expanded form. 

 C. capillata will live for many hours when under the influence of strychnia, 

 but eventually death supervenes. The animal dies in full diastole. 



(d) Curare was administered by the following method. I placed the 

 Medusa in a flat- shaped beaker filled to the brim with sea- water. This 

 beaker I then placed in a large basin filled with sea- water up to the level 

 of the water in the beaker. Having next divided the Medusa across its 

 whole diameter, with the exception of a small piece of marginal tissue to 

 act as a connecting-link between the two resulting halves, I transferred 

 one of these halves to the water in the basin, leaving the other half still 

 in the beaker. Lastly, I poisoned the water in the beaker with successive 

 doses of urari solution. The species best suited for this experiment is 

 Staurojphora laciniata. 



The effects of curare thus administered are most marked and beautiful. 

 Previous to the administration of the poison both halves of the divided 

 Medusa are, of course, contracting vigorously — the contractile waves now 



