﻿310 
  PROFESSORS 
  EDWARD 
  FORBES 
  AND 
  J. 
  GOODSIR 
  ON 
  SOME 
  

  

  In 
  the 
  synopsis 
  of 
  the 
  genera 
  of 
  zoophytes, 
  by 
  Milne 
  Edwards 
  and 
  Haime, 
  

   the 
  genus 
  Sarcodictyon 
  is 
  placed 
  in 
  the 
  family 
  Cornularince, 
  among 
  the 
  Alcy- 
  

   onaria. 
  We 
  can 
  hardly 
  assent 
  to 
  its 
  removal 
  from 
  the 
  immediate 
  neighbourhood 
  

   of 
  Alcyonium, 
  for 
  it 
  differs 
  merely 
  in 
  the 
  stoloniferous 
  method 
  of 
  growth. 
  The 
  

   new 
  species 
  now 
  announced, 
  goes 
  far 
  to 
  confirm 
  our 
  view 
  of 
  its 
  affinities. 
  This 
  

   genus 
  may 
  be 
  said 
  to 
  bear 
  much 
  the 
  same 
  relation 
  to 
  Alcyonium, 
  which 
  our 
  new 
  

   genus 
  Syntethys 
  (among 
  the 
  Ascidians) 
  bears 
  to 
  Clavelina. 
  

  

  Arachnactis 
  albida. 
  Sars. 
  — 
  In 
  the 
  first 
  part 
  of 
  the 
  very 
  beautiful 
  and 
  valu- 
  

   able 
  work 
  by 
  M. 
  Sars, 
  entitled 
  " 
  Fauna 
  Littoralis 
  Norvegise," 
  published 
  at 
  Chris- 
  

   tiania 
  in 
  1846, 
  a 
  new 
  genus 
  and 
  species 
  of 
  Helianthoid 
  zoophytes 
  is 
  described 
  at 
  

   length, 
  and 
  figured 
  in 
  detail, 
  under 
  the 
  name 
  of 
  Arachnactis 
  albida. 
  

  

  In 
  the 
  " 
  Travels 
  in 
  Lycia," 
  by 
  Professor 
  E. 
  Forbes 
  and 
  Captain 
  Spratt, 
  R.N., 
  

   published 
  in 
  1847, 
  a 
  swimming 
  Actinea 
  is 
  noticed 
  and 
  figured 
  from 
  the 
  Egean. 
  

   This 
  was 
  clearly 
  a 
  species 
  of 
  Arachnactis. 
  

  

  When 
  Dr 
  Balfour 
  visited 
  the 
  Island 
  of 
  Lewis 
  with 
  his 
  pupils 
  in 
  August 
  1841 
  , 
  

   they 
  procured 
  a 
  number 
  of 
  mutilated 
  specimens 
  of 
  a 
  radiate 
  animal 
  found 
  floating 
  

   in 
  the 
  Minch. 
  These 
  were 
  too 
  imperfect 
  for 
  determination 
  at 
  the 
  time. 
  This 
  year, 
  

   however, 
  we 
  have 
  discovered 
  a 
  species 
  of 
  A 
  rachnactis 
  evidently 
  identical 
  with 
  

   the 
  Norwegian 
  one 
  in 
  the 
  Minch, 
  and 
  the 
  remains 
  of 
  Dr 
  Balfour's 
  animal 
  have 
  

   proved 
  identical 
  with 
  it. 
  

  

  The 
  definition 
  of 
  the 
  genus 
  given 
  by 
  Sars 
  is, 
  — 
  " 
  Animal 
  liberum, 
  molle, 
  

   natans 
  ; 
  corpus 
  breviter 
  cylindricum, 
  parvum, 
  basi 
  rotundata, 
  disco 
  suctorio 
  

   carente 
  ; 
  os 
  seriebus 
  tentaculorum 
  non 
  retractilium 
  duabus 
  circumdatum, 
  exte- 
  

   rioribus 
  longissimis, 
  interioribus 
  brevibus." 
  

  

  The 
  number 
  of 
  the 
  larger 
  tentacula 
  were 
  eight 
  to 
  ten, 
  of 
  the 
  smaller, 
  accord- 
  

   ing 
  to 
  Sars, 
  twelve 
  ; 
  we 
  have 
  observed 
  them 
  as 
  many 
  as 
  sixteen. 
  The 
  shape 
  of 
  

   the 
  body 
  is 
  pyriform 
  ; 
  its 
  colour 
  dusky 
  white, 
  tinged 
  with 
  tawny. 
  The 
  outer 
  

   tentacula 
  are 
  very 
  long, 
  tawny 
  and 
  white 
  ; 
  the 
  inner, 
  much 
  shorter. 
  The 
  length 
  

   of 
  the 
  body 
  is 
  about 
  one 
  inch. 
  The 
  outer 
  tentacula 
  can 
  be 
  extended 
  to 
  three 
  or 
  

   four 
  times 
  the 
  length 
  of 
  the 
  body. 
  The 
  creature 
  swims 
  freely, 
  and 
  habitually 
  in 
  

   the 
  manner 
  of 
  a 
  medusa. 
  

  

  There 
  is 
  a 
  point, 
  however, 
  of 
  consequence 
  which 
  Sars 
  did 
  not 
  observe, 
  it 
  can 
  

   convert 
  its 
  posterior 
  extremity 
  into 
  a 
  suctorial 
  disk, 
  and 
  fix 
  itself 
  to 
  bodies 
  in 
  the 
  

   manner 
  of 
  an 
  Actinea. 
  Aristotle 
  states 
  in 
  several 
  places 
  in 
  his 
  History 
  of 
  Ani- 
  

   mal, 
  that 
  the 
  Actinea 
  {axaMyn) 
  can 
  detach 
  itself 
  from 
  the 
  rock 
  and 
  swim. 
  Thus, 
  

   in 
  Book 
  iv. 
  6, 
  speaking 
  of 
  these 
  animals, 
  he 
  writes, 
  — 
  " 
  vgoevtyvxe 
  && 
  yag 
  ruig 
  mrga/s 
  

   u<mg 
  hia 
  raiv 
  bergaxodsg/iw, 
  ccnroxUrai 
  s 
  Man." 
  Commentators 
  have 
  supposed 
  that 
  he 
  

   confounded 
  Actinese 
  with 
  Medusae. 
  But 
  he 
  mentions 
  the 
  latter 
  animals 
  under 
  

   another 
  name. 
  The 
  discovery 
  of 
  the 
  Arachnactis, 
  and 
  its 
  abundance 
  in 
  the 
  

   Grecian 
  seas 
  explain 
  the 
  difficulty, 
  and 
  shew 
  the 
  accuracy 
  of 
  his 
  observations. 
  

  

  Plancia. 
  New 
  Genus. 
  — 
  Umbrella 
  hemispherical 
  ; 
  radiating 
  vessels 
  four, 
  

  

  