32 GEOEGE JOHN EOMANES 1875- 



respond to local stimulus throughout its substance 

 when so severely cut), and, on the other hand, the 

 supposition of a nervous plexus (for this would 

 require to be so very intricate, and the hypothesis of 

 scattered cells is without microscopical evidence here 

 or elsewhere). I think, therefore, that we are driven 

 to conclude that the muscular tissue of Medusae, 

 though more differentiated into fibres than is the 

 contractile tissue of the snail's heart, is, as much as 

 the latter, an instance of 'physiological continuity.' 

 (Whether or not the interfascicular protoplasmic 

 substance before spoken of is the seat of this physio- 

 logical continuity is here immaterial.) Dr. Foster 

 fully agrees with me in this deduction from my ex- 

 periments, and is very pleased about the latter, thus 

 affording additional support to his views. But what 

 I want to ask you is, supposing the interfascicular 

 substance to have no share in conducting stimulus 

 (and I have no evidence of its presence in Sarsia), 

 and hence that the properties of nerve and muscle 

 are united in the contractile fibres of Medusae sup- 

 posing this, do you think that the peculiarity you 

 observed in the molecular conformation of this tissue, 

 considered as muscular, is likely to have anything to 

 do with this peculiarity in its function ? 



I know you do not like theory, so I shall return 

 to fact. There can be no doubt whatever that the 

 seat of spontaneity is as much localised in the 

 margin as the sensibility to stimulus is diffused 

 throughout the bell. There must, therefore, be some 

 structural difference in the tissue here to correspond 

 to this great functional difference. Agassiz is very 



