NO.    5      MALE  GENITALIA  OF  ORTHOPTEROID  INSECTS SNODGRASS        65 
The  so-called  parameres  of  the  Tettigoniidae  are  supposed  to  repre- 
sent the  paired  right  and  left  phallic  lobes  of  Blattidae,  but,  as  will 
presently  be  shown,  the  development  of  the  tettigoniid  phallus  does  not 
warrant  the  assumption  of  a  close  homology  between  any  of  its  minor 
parts  and  the  phallic  structures  of  Blattidae. 
Though  the  tettigoniid  phallus  is  ordinarily  concealed  within  the 
genital  chamber,  the  entire  organ  is  protractile.  In  the  protracted 
condition  (fig.  22  E)  the  dorsal  cavity  with  its  armature  is  everted, 
and  all  parts  of  the  phallus  may  be  so  greatly  distended  by  blood 
pressure  that  the  organ  assumes  an  entirely  different  appearance  from 
that  of  its  passive  state.  The  principal  muscles  of  the  phallus  are  a 
pair  of  dorsal  retractors  (fig.  24  B,  rpd)  arising  on  the  lateral  parts 
of  the  tenth  abdominal  tergum,  and  a  pair  of  ventral  retractors  {rpv) 
arising  on  the  ninth  sternum. 
The  development  of  the  tettigoniid  phallus  in  nymphal  instars  shows 
that  the  adult  organ  is  a  composite  structure  formed  by  the  union  of 
several  primary  lobes  of  the  genital  integument  that  grow  out  around 
the  gonopore,  or  mouth  of  the  invagination  that  gives  rise  to  the 
ectodermal  part  of  the  ejaculatory  duct.  In  a  young  nymph  of  Cono- 
cephalus  fasciatus,  9  mm  in  length  (fig.  23  A),  the  gonopore  is  sur- 
rounded by  six  small  phallic  lobes  (B,  C),  two  of  which  are  dorsal, 
two  lateral,  and  two  ventral.  These  simple  lobes,  or  phallomeres, 
enclose  between  them  a  shallow  endophallic  cavity,  to  the  base  of 
which  is  attached  the  ejaculatory  duct.  The  early  nymphal  phallomeres 
of  Conoccphalus  thus  resemble  the  nymphal  phallomeres  of  Blatta  or 
Pcriplaneta  (figs.  12  E,  15  C),  except  that  there  are  six  of  them 
instead  of  three.  At  this  stage,  therefore,  it  is  impossible  to  identify 
any  particular  pair  of  lobes  in  Conocephahis  with  any  particular  pair 
in  Blatta  or  Pcriplaneta.  At  a  later  stage  in  the  development  of  Cono- 
cephahis, in  a  nymph  11  mm  long  (fig.  23  D),  the  two  primary  dorsal 
phallomeres  have  united  in  a  single  broad  dorsal  lobe  (E,  dl),  and  the 
two  ventral  phallomeres  have  united  in  a  single  ventral  lobe  (E,  F, 
vl) ,  the  lateral  lobes  {II)  retaining  their  independence.  All  the  lobes, 
moreover,  are  now  carried  out  on  a  common  basal  ring,  and  the  endo- 
phallic cavity  is  correspondingly  deepened.  Thus  is  established  the 
typical  four-lobed  structure  of  the  adult  phallus,  but  the  special 
features  of  the  dorsal  lobe  are  not  yet  in  evidence.  At  a  still  later 
stage,  in  a  nymph  14  mm  in  length,  the  basal  part  of  the  phallus  has 
greatly  lengthened  (G),  so  that  the  primary  phallomeres  now  appear 
as  relatively  small  terminal  lobes,  with  the  wide  phallotreme  between 
them.  The  dorsal  lobe  (dl)  still  presents  a  broad  flat  upper  surface, 
but  there  are  dififerentiated  upon  it  two  oval  thickenings  {h),  which 
