﻿BASALS 
  OF 
  EtTGENIACRINID^. 
  361 
  

  

  of 
  this 
  ring-canal 
  the 
  secondary 
  branches 
  continue 
  to 
  converge 
  more 
  

   slowly, 
  and 
  do 
  not, 
  as 
  a 
  rule, 
  meet 
  to 
  form 
  one 
  radial 
  canal 
  until 
  

   just 
  before 
  the 
  upper 
  articulating 
  surface 
  of 
  the 
  first 
  radial 
  is 
  

   reached. 
  This 
  arrangement, 
  of 
  which 
  the 
  weathered 
  specimens 
  

   alone 
  afford 
  sufficient 
  proof, 
  has 
  been 
  confirmed 
  by 
  Prof. 
  v. 
  Zittel 
  

   from 
  the 
  evidence 
  of 
  thin 
  transverse 
  sections. 
  

  

  The 
  argument 
  as 
  to 
  the 
  position 
  of 
  the 
  basals, 
  founded 
  on 
  the 
  

   evidence 
  thus 
  afforded, 
  is 
  as 
  follows 
  : 
  — 
  In 
  every 
  Crinoid 
  in 
  which 
  the 
  

   course 
  of 
  these 
  canals 
  has 
  been 
  traced, 
  with 
  the 
  exception 
  of 
  Bathy- 
  

   crinus, 
  the 
  axial 
  canal 
  passes 
  up 
  into 
  the 
  basals, 
  and 
  there 
  gives 
  off 
  

   five 
  interradial 
  canals 
  ; 
  these 
  interradial 
  canals 
  branch 
  during 
  their 
  

   passage 
  through 
  the 
  basals 
  ; 
  the 
  secondary 
  branches 
  pass 
  into 
  the 
  

   radials, 
  and 
  there 
  the 
  adjacent 
  secondary 
  branches 
  unite 
  into 
  radial 
  

   canals. 
  In 
  Baihycrinus 
  the 
  interradial 
  canals 
  are 
  likewise 
  given 
  

   off 
  into 
  the 
  basals, 
  and 
  the 
  only 
  difference 
  is 
  that 
  they 
  pass 
  some 
  

   little 
  distance 
  up 
  between 
  the 
  radials 
  before 
  diverging 
  into 
  secon- 
  

   dary 
  branches. 
  The 
  induction 
  therefore 
  is 
  that 
  the 
  basals 
  invariably 
  

   contain 
  the 
  interradial 
  canals, 
  and, 
  conversely, 
  that 
  the 
  position 
  of 
  

   the 
  interradial 
  canals 
  indicates 
  that 
  of 
  the 
  basals. 
  In 
  Eugenia- 
  

   crinus 
  the 
  interradial 
  canals 
  originate 
  in 
  the 
  middle 
  of 
  the 
  radial 
  

   circlet 
  ; 
  we 
  therefore 
  infer 
  that 
  the 
  basals 
  have 
  passed 
  up 
  between 
  

   the 
  radials, 
  and 
  as 
  we 
  can 
  find 
  no 
  actual 
  trace 
  of 
  them, 
  we 
  must 
  

   suppose 
  that 
  they 
  have 
  been 
  absorbed 
  by 
  the 
  radials. 
  Or 
  perhaps, 
  

   as 
  Prof. 
  v. 
  Zittel 
  writes 
  in 
  his 
  letter 
  of 
  December 
  24, 
  1888 
  : 
  — 
  

   " 
  Die 
  Basis 
  muss 
  somit 
  durch 
  Ueberwucherung 
  der 
  liadialia 
  ganz 
  

   nach 
  oben 
  gedrlingt 
  worden 
  sein, 
  und 
  bildet 
  wahrscheinlich 
  im 
  

   Grande 
  des 
  Kelches 
  eine 
  kleine 
  Eosette, 
  wie 
  bei 
  Antedon" 
  

  

  To 
  obviate 
  certain 
  difficulties 
  which 
  this 
  view 
  appears 
  to 
  some 
  to 
  

   present, 
  it 
  might 
  possibly 
  be 
  argued 
  that 
  Eugeniacrinus 
  is 
  arranged 
  

   on 
  an 
  extension 
  of 
  the 
  Bathycrinus 
  type. 
  In 
  other 
  words, 
  that 
  the 
  

   top 
  stem-joint 
  is, 
  as 
  Carpenter 
  supposed, 
  the 
  homologueof 
  the 
  fused 
  

   basal 
  ring, 
  and 
  that 
  the 
  axial 
  canal 
  passes 
  right 
  through 
  this, 
  iuto 
  

   the 
  radials, 
  before 
  branching. 
  This 
  explanation 
  would 
  perhaps 
  be 
  

   more 
  anomalous 
  than 
  the 
  anomaly 
  it 
  explained 
  ; 
  but, 
  apart 
  from 
  

   that, 
  the 
  assumption 
  has 
  nothing 
  to 
  support 
  it. 
  On 
  the 
  contrary, 
  

   in 
  Bathycrinus, 
  as 
  in 
  Rhizocrinus, 
  which 
  approaches 
  it 
  in 
  this 
  

   respect, 
  there 
  are 
  no 
  interradial 
  commissures 
  ; 
  the 
  need 
  for 
  them 
  

   seems 
  to 
  have 
  vanished 
  owing 
  to 
  the 
  very 
  high 
  point 
  at 
  which 
  the 
  

   interradial 
  canals 
  branch 
  ; 
  in 
  fact 
  the 
  branches 
  themselves 
  act 
  as 
  

   commissures. 
  But 
  in 
  Eugeniacrinus 
  there 
  is 
  evidence 
  of 
  these 
  in- 
  

   terradial 
  commissures 
  ; 
  the 
  ring-canal 
  was 
  complete 
  ; 
  the 
  arrange- 
  

   ment 
  was 
  more 
  primitive 
  than 
  that 
  of 
  Bathyc?*inus, 
  and 
  no 
  argument 
  

   from 
  analogy 
  can 
  hold 
  good. 
  

  

  If 
  any 
  recent 
  form 
  is 
  to 
  be 
  compared 
  with 
  Eugeniacrinus, 
  it 
  must 
  

   be 
  Holopus 
  ; 
  for 
  the 
  Holopodidas 
  are 
  by 
  all 
  placed 
  close 
  to 
  the 
  

   Eugeniacrinidae. 
  Here 
  unfortunately 
  the 
  evidence 
  is 
  incomplete 
  ; 
  

   but, 
  such 
  as 
  it 
  is, 
  it 
  lends 
  no 
  countenance 
  to 
  the 
  idea 
  that 
  the 
  rela- 
  

   tion 
  of 
  the 
  canals 
  to 
  the 
  calyx 
  follows 
  the 
  arrangement 
  that 
  

   obtains 
  in 
  the 
  Bourgueticrinidaa. 
  The 
  extinct 
  fossil 
  Holopodidae 
  

   throw, 
  no 
  further 
  light 
  on 
  this 
  question. 
  At 
  the 
  same 
  time 
  such 
  

  

  