﻿DKVELOPMRNT 
  AND 
  METAMORPHOSIS. 
  

  

  95 
  

  

  notochord 
  is 
  thus 
  completely 
  surrounded 
  by 
  a 
  thick 
  

   sheath 
  in 
  tadpoles 
  with 
  imperfectly 
  developed 
  limbs. 
  

   This 
  mode 
  of 
  formation 
  of 
  both 
  the 
  arch 
  and 
  the 
  

   greater 
  part 
  or 
  whole 
  of 
  the 
  so-called 
  centrum 
  from 
  

   the 
  same 
  cartilage 
  explains 
  why 
  there 
  is 
  never 
  a 
  

   neuro-central 
  suture 
  in 
  these 
  Batrachians. 
  

  

  Fig. 
  39. 
  

  

  Side 
  view 
  of 
  cartilaginous 
  skeleton 
  of 
  tadpole 
  

   with 
  outlines 
  of 
  the 
  external 
  parts. 
  

  

  A. 
  Anus. 
  

  

  K 
  Eye. 
  

   M. 
  Mouth. 
  

  

  N. 
  Nostril. 
  

  

  S. 
  Spiraculum. 
  

  

  as. 
  Astragalus. 
  

  

  ca. 
  Calcaneum. 
  

  

  ch. 
  Chorda. 
  

  

  cliy. 
  Ceratohyal. 
  

  

  cor. 
  Coracoid 
  and 
  

   prsecoracoid. 
  

  

  /. 
  Femur. 
  

  

  fi. 
  Fibula. 
  

  

  h. 
  Humerus. 
  

  

  II. 
  Lower 
  labial. 
  

  

  771. 
  Manus. 
  

   me. 
  Meckelian. 
  

  

  of 
  Bomhinator 
  pachypus, 
  

   (After 
  Goette.) 
  

  

  ov. 
  Occipital 
  vertebra. 
  

  

  p. 
  Pes, 
  

   pe. 
  Pelvis. 
  

   ru. 
  Radius-ulna. 
  

   sc. 
  Scapula. 
  

   su. 
  Suspensorium. 
  

  

  t. 
  Tibia. 
  

   ul. 
  Upper 
  labial. 
  

  

  V. 
  Yertebra. 
  

  

  During 
  segmentation 
  of 
  the 
  dorsal 
  cartilages 
  men- 
  

   tioned 
  above, 
  which 
  send 
  out 
  the 
  transverse 
  pro- 
  

   cesses 
  or 
  diapophyses, 
  there 
  appears 
  between 
  each 
  two 
  

   centra 
  an 
  intervertebral 
  cartilage, 
  out 
  of 
  which 
  the 
  

   articulating 
  knob 
  of 
  the 
  centrum 
  is 
  formed, 
  and 
  be- 
  

   comes 
  attached 
  either 
  to 
  the 
  vertebra 
  anterior 
  (pro- 
  

   coelous 
  type) 
  or 
  posterior 
  (opisthocoelous 
  type) 
  to 
  it, 
  

   if 
  not 
  remaining 
  as 
  an 
  independent, 
  intervertebral, 
  

   ossified 
  sphere, 
  as 
  we 
  sometimes 
  find 
  in 
  specimens 
  of 
  

   Pelohatidse. 
  Ossification 
  appears 
  first 
  in 
  the 
  neural 
  

   arch, 
  next 
  descends 
  to 
  the 
  centrum, 
  and 
  sets 
  in 
  last 
  

   in 
  the 
  articulating 
  condyle. 
  

  

  