28  SMITHSONIAN    MISCELLANEOUS    COLLECTIONS  VOL.    g6 
nymphal  blattids  (fig.  12  E)  ;  but  in  the  forms  in  which  the  lobes 
are  partly  united  (fig.  8  H,  I),  the  phallic  organ  of  an  adult  phasmatid 
comes  near  being  a  replica  of  the  nymphal  organs  in  Tettigoniidae 
(fig.  23  E). 
The  tenth  abdominal  segment  is  always  well  developed  and  usually 
extends  beyond  the  genital  parts  as  a  conical  or  oval  end-segment 
of  the  body  bearing  the  cerci  and  the  anus  (fig.  8  C,  J,  L,  X),  but  in 
Timema  (A)  it  is  relatively  short  and  the  ninth  sternum  projects 
beneath  it.  The  tenth  sternum  may  be  a  simple  plate  extending  back- 
ward to  the  anal  region  (J,  L,  A'.S")  ;  its  posterior  margin  is  some- 
times cleft,  the  two  points  being  continuous  dorsally  with  the  para- 
procts.  In  many  of  the  phasmatids,  however,  the  venter  of  the  tenth 
segment  of  the  male  abdomen  bears  a  large  sclerotic  lobe  extended 
horizontally  backward  from  its  anterior  margin,  and  is  otherwise 
membranous.  This  ventral  lobe  of  the  tenth  segment  is  known  as  the 
vomer  (C,  Vo).  The  vomer  varies  greatly  in  size  and  shape  in 
different  species  of  phasmatids ;  an  elaborate  account  of  its  numerous 
modifications  is  given  by  Pantel  (1915),  and  both  De  Sinety  (1901) 
and  Pantel  show  that  the  organ  is  developed  during  nymphal  stages 
as  a  fold  of  the  venter  of  the  tenth  abdominal  segment.  In  the  ex- 
ample here  given,  Anisomorpha  hiiprestoides,  the  vomer  is  a  broad, 
strongly  sclerotic  plate  (D,  Vo)  armed  distally  with  several  small 
spines,  and  ending  with  an  asymmetrical  point  curved  upward  between 
the  paraprocts  (C).  Its  basal  angles  are  produced  into  inflections 
of  the  body  wall  as  a  pair  of  strong  divergent  apodemes  (E,  Ap), 
each  provided  with  a  thick  muscle  (mcl)  arising  on  the  tenth  tergum. 
The  ends  of  the  apodemes  appear  to  be  fulcral  points  applied  against 
the  tergal  walls.  The  vomer  might  be  supposed  to  be  an  instrument  for 
depressing  the  subgenital  plate  of  the  female,  but  its  asymmetry 
and  the  spinous  armature  of  its  distal  part  do  not  appear  to  adapt 
it  to  such  a  purpose. 
The  eleventh  segment  is  inconspicuous,  though  it  bears  the  cerci, 
which  are  usually  large  and  prominent.  It  consists  of  a  small  epiproct 
(fig.  8  K,  Eppt)  projecting  above  the  anus  from  beneath  the  margin 
of  the  tenth  tergum  {XT),  and  of  two  soft  paraproctial  lobes  (Papt) 
lying  at  the  sides  of  the  anus,  either  vertical  or  more  or  less  horizontal 
in  position.  The  cerci  are  generally  of  a  simple  cylindrical  form  (C, 
D,  Cer),  but  they  vary  much  in  size,  and  may  be  long,  falcate  clasping 
organs  (K,  L).  or  sometimes  foliaceous  or  branched  structures.  They 
are  movable  by  large  muscles  arising  on  the  tergum  of  the  tenth 
segment  (L).  In  Timema  calif oniica  the  cerci  have  an  exceptional 
development,  being  strong,  asymmetrical  appendages  curved  toward 
