On the Locomotor System of Medusae. 253 



o that shortly after they first set iu the period of diastole is very 

 much prolonged aud 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. Recovery in normal 

 sea-water is very rapid, occuppng only a few seconds in the case of 

 Sars'ta ; but, like the reverse process of ansesthesiation, it is clearly 

 of a gradual nature. 



(b) Morphia is as decided in its action upon Medusae as is chlo- 

 roform. The processes of anaesthesiation and of subsequent re- 

 covery are very similar to those just described, except that both 

 processes occupy a some\^'hat longer time. 



(c) 8trych\ia exerts a very marked influence upon Medusae. Of 

 the species I have met with Ci/aiuea cdjiillata 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 ani- 

 mal are as regular as are those of a heart. Shortly after a solu- 

 tion 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 irregularity then in- 

 creases 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 

 contractions, amounting, in fact, to nothing less than tonic spasms. 

 It is further of importance to remark that the convulsions are very 

 plai)ily of a paroxysmal nature — prolonged pei'iods of uninter- 

 rupted 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 wiW. 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 b(>aker 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 be- 

 tween 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 iu the beaker with successive doses of 

 iirari solution. The species best suited for this experiment is 

 Stauropliora laciniata. 



The effects of curare thus administered are most marked and 

 beautiful. Previous to theadmiuistratiou of the poison both halves 

 of the divided Medusa are, of course, contracting vigorously — the 

 contractile waves bow running from the half in the basin to the 

 half in the beaker, and jm}\v vice versa. Hut affer the half in the 

 beaker has been cffectuaily poisoned all motion in it completely 

 ceases, the unpoisoncd halt, however, continuing to contract inde- 

 pendently. If the poisoned half be now irritated, by nii)ping with 



