[    221  ] 
XXV.  On  the  Young  of  the  Ornithorhynchus  paradoxus,  Blum.  By  Richard  Owen, 
Esq.,  F.Z.S.,  Assistant  Conservator  of  the  Museum  of  the  Royal  College  of  Surgeons 
in  London. 
Communicated  May  27,  ]834. 
It  must  be  gratifying  to  every  friend  of  Natural  History  to  perceive  how  rapidly,  by 
the  exertions  of  enlightened  travellers,  the  different  facts  and  materials  are  accurau- 
lating  which  tend  towards  the  complete  elucidation  of  the  economy  and  natural  affini- 
ties of  the  Monotrematous  Quadrupeds. 
On  a  retrospect  of  the  history  of  these  anomalous  animals,  we  find  in  the  year  ]  829 
the  sum  of  what  w^as  then  certainly  known  as  to  their  generative  function  thus  expressed 
by  Cuvier  :  "  Comme  enfin  on  n'est  pas  encore  unanime  sur  I'existence  de  leurs  ma- 
melles,  on  en  est  a  savoir  si  ces  animaux  sont  vivipares^  ou  ovipares."^  Such  was  the 
condition  in  which  this  question  was  left,  notwithstanding  the  valuable  labours  of 
Meckel  and  M.  Geoffroy,  and  such  the  received  opinion  as  to  the  essential  nature  of 
the  connexion  between  lactation  and  placental  generation. 
It  appears  to  have  been  under  this  impression  that  the  revival  of  Meckel's  doc- 
trine in  1832  was,  on  the  one  hand,  regarded,  though  erroneously,  as  proof  of  the  vivi- 
parous generation  of  the  Ornithorhynchus'^,  and  on  the  other  hand,  as  strenuously  opposed 
by  those  Naturalists  who  had  adopted  the  oviparous  theory,  and  who  regarded  the  Mo- 
notremata  as  a  distinct  class  of  Vertebrata.  The  true  theory  will  in  all  probability  be 
found  somewhere  between  these  extremes.  Of  all  known  Mammalia,  the  Edentulous 
Marsupiata  undoubtedly  approximate  most  closely  the  oviparous  type.  But  if  we  except 
the  partial  atrophy  of  the  right  moiety  of  the  female  organs,  and  the  form  of  the  mouth 
of  the  Ornithorhynchus,  all  the  principal  deviations  from  the  mammiferous  type,  as  ex- 
hibited in  the  skeleton  and  in  the  composition  of  the  entire  generative  apparatus,  indi- 
cate the  affinity  of  the  Monotremata  to  the  Reptilia  rather  than  to  the  Aves  ;  and  all 
the  well  ascertained  facts  respecting  their  generation  support  the  inference,  that,  as  in 
many  Reptiles,  the  germ  is  developed  within  the  body  of  the  parent  unaided  by  the  for- 
mation of  a  placenta. 
>  That  there  might  be  no  mistake  as  to  the  sense  in  which  this  word  is  used,  Cuvier  previously  defines  it. 
"  Dans  tous  les  Mammif^res  la  generation  est  essentiellement  vivipare  ;  c'est  a  dire  que  le  foetus,  immediatement 
apres  la  conception,  descend  dans  la  matrice,  enferme  dans  ses  enveloppes,  dont  la  plus  ext^rieure  est  nomm^e 
chorion,  et  I'interieure  amnios  ;  il  se  fixe  aux  parois  de  cette  cavite  par  un  ovi  plusieurs  plexus  de  vaisseaux, 
appeles  placenta,  qui  etablissent  entre  lui  et  sa  mere  une  communication,  d'ou  il  tire  sa  nourriture,  et  probable- 
ment  aussi  son  oxygenation." — Regne  Animal,  tom.  i.  p.  64.  "  Ibid.,  p.  234. 
2  G  2 
