ARE NERVES EVER " DIFFUSED " ? 75 



to talk of this thiiio: as " difFiised/' is to talk of it as 

 wanting one of its constituent characters ; it is like 

 talking of fluid crystals, or square circles. All this 

 Dr Williams, I am sure, would be the first to admit, 

 for he doubts the existence of nerves even in the 

 Echinodermata ; and I would ask him whether the 

 tentacles of the Terebella are not assumed to have 

 muscles, in accordance with the cm-rent notions that 

 wherever there is Contractility the existence of mus- 

 cles must be inferred ? I put the question as a ques- 

 tion merely. My own observations utterly failed to 

 detect muscular fibres in the tentacles of the spe- 

 cies I examined. On one occasion, indeed, they pre- 

 sented the aspect of circular fibres, which I thought 

 must be the muscles Dr Williams refers to ; but, 

 on applying a power of 300 diameters, these fibres 

 resolved themselves into simple corrugations of the 

 investing membrane ; and I can very confidently 

 assert that in no single species of Terebella which has 

 fallen in my way was there the slightest trace of 

 muscle. 



But enough of anatomy for this morning ! The 

 lovely lanes of Ilfracombe invite us, and we may cool 

 our over-heated brows by a delicious breeze blowing- 

 over the Tors ; or perhaps the noble sweep of Tenby 

 sands seduces us to walk to Giltar Point. A bottle or 

 two will be useful in either expedition ; a small basket 

 will be worth the trouble of carriasje if we take the 

 sands, for there was a gale last night, and who knows 

 what may have been thrown up by it ? And if you 



