1875 EXPEBIMENTS ON MEDUSJE 19 



possessed a visual sense localised in their marginal 

 sense organs. 



The effects of electrical stimulation agreed in all 

 respects with those produced on the excitable tissues 

 of other animals. He next experimentally investi- 

 gated in the jelly-fish the paths along which the 

 nervous impulses must pass in their passage from the 

 locomotor centres, where they originate, to the general 

 contractile tissues of the animal. 



The results of these experiments led him to infer 

 the existence of a very fine plexus of nerve fibres, in 

 which the constituent threads cross and re-cross one 

 another without actually coalescing. This conclusion, 

 which he arrived at from purely experimental grounds, 

 was some years afterwards confirmed by minute his- 

 tological research. 



Finally, the effect of various poisons, chloroform, 

 alcohol, &c, was tried, and the striking resemblance 

 of their action on the nervous system of the Medusae 

 with that which they exert on that of higher animals 

 supports the belief that nerve tissue when it first 

 appears in the scene of life has the same fundamental 

 properties as it has in higher animals. 



This piece of work was important, as the facts 

 threw light, as Professor Sanderson has said, on ele- 

 mentary questions of physiology relating to excita- 

 bility and conduction, and it was a characteristic of 

 Mr. Eomanes that in all his work, of whatever kind, 

 he was always searching for principles. The minutest 

 detail never escaped his attention if it appeared at all 

 likely in any way to throw light on some biological 

 or psychological problem. Only a trained scientific 

 worker can appreciate the amount of labour these 

 Royal Society papers represented. In 1875 he gave 



o2 



