224 
MR.  R.  OWEN  ON  THE  YOUNG  OF 
The  situation  of  the  exterior  nostrils  has  already  been  given  ;  they  communicate  with 
the  mouth  by  the  foramina  incisiva,  which  are  situated  at  nearly  3  lines'  distance  from 
the  end  of  the  upper  mandible,  and  are  each  guarded  by  a  membranous  fold  extending 
from  their  anterior  margin :  the  nasal  cavity  then  extends  backwards,  and  terminates 
immediately  above  the  larynx,  the  tip  of  the  epiglottis^  extending  into  it,  and  resting 
upon  the  soft  palate. 
On  the  middle  line  of  the  upper  mandible,  and  a  little  anterior  to  the  nostrils,  there 
is  a  minute  fleshy  eminence  lodged  in  a  slight  depression.  In  the  smaller  specimen 
this  is  surrounded  by  a  discontinuous  margin  of  the  epidermis,  with  which  substance, 
therefore,  and  probably  (from  the  circumstance  of  its  being  shed)  thickened  or  horny, 
the  caruncle  had  been  covered.  It  is  a  structure  of  which  the  upper  mandible  of  the 
adult  presents  no  trace,  and  is  obviously  analogous  to  the  horny  knob  which  is  observed 
on  the  upper  mandible  in  the  foetus  of  some  Birds.  I  do  not,  however,  conceive  that 
this  structure  is  necessarily  indicative  of  the  mandible's  having  been  applied,  under  the 
same  circumstances,  to  overcome  a  resistance  of  precisely  the  same  kind  as  that  for 
which  it  is  designed  in  the  young  Birds  which  possess  it.  The  shell-breaking  knob  is 
found  in  only  a  part  of  the  class ;  and  although  the  similar  caruncle  in  the  Ornitho- 
rhynchus  affords  a  curious  additional  affinity  to  the  Aves,  yet  as  all  the  known  history 
of  the  ovum  points  strongly  to  its  ovoviviparous  development,  the  balance  of  evidence 
is  still  in  favour  of  this  theory. 
The  situation  of  the  eyes  was  indicated  by  the  convergence  of  a  few  wrinkles  to  one 
point ;  but  when,  even  in  the  larger  of  the  two  specimens,  these  were  put  upon  the 
stretch,  the  integument  was  found  entire,  and  completely  shrouding  or  covering  the 
eyeball  anteriorly.  This  fact  is  one  of  great  importance  to  the  question  of  the  mam- 
miferous  character  of  the  Ornithorhynchus.  For  on  the  supposition  of  the  young  animal 
possessing  locomotive  faculties,  which  would  enable  it,  like  the  young  Gosling,  imme- 
diately after  birth  or  exclusion,  to  follow  the  parent  into  the  water,  and  there  to  receive 
its  nutriment  (whether  mucous  or  otherwise) ,  the  sense  of  vision  ought  certainly  to  be 
granted  to  it  in  order  to  direct  its  movements.  The  privation  of  this  sense,  on  the 
contrary,  implies  a  confinement  to  the  nest,  and  a  reception  on  land  of  the  mammary 
secretion  of  the  parent. 
The  general  form  of  the  body,  and  the  cartilaginous  condition  of  the  bones  of  the 
extremities,  equally  militate  against  the  young  Ornithorhynchus  possessing  at  this  period 
of  its  existence  active  powers  of  swimming  or  creeping.  The  head  and  tail  are  closely 
approximated  on  the  ventral  aspect,  requiring  force  to  pull  the  body  out  into  a  straight 
line ;  and  the  relative  quantity  of  integument  on  the  back  and  belly  shows  that  the 
position  necessary  for  the  due  progressive  motions  is  unnatural  at  this  stage  of  growth. 
The  form  of  the  young  Kangaroo  soon  after  birth  is  very  similar  to  this,  which  is  com- 
mon to  the  foetus  both  of  the  viviparous  and  oviparous  classes. 
1  The  epujlotlis  is  essentially  associated  with  lactation,  not  with  viviparous  generation. 
