NO.    5      MALE  GENITALIA  OF  ORTHOPTEROID  INSECTS — SNODGRASS        49 
The  phallic  organs  of  Blattella  in  the  retracted  state  are  shown  as 
seen  from  above  at  E  of  figure  i6.  The  anterior  wall  of  the  genital 
chamber  {x-x)  runs  obliquely  forward  from  left  to  right.  On  the 
left  it  is  produced  into  a  deep  pouch  (^r)  containing  the  hooked  left 
phallomere  {IPhm)  ;  on  the  right  it  forms  a  wider  but  shallower 
pocket  (y)  containing  the  right  phallomere.  The  right  phallomere 
consists  principally  of  a  flattened  sclerotic  arm  (rPhin),  which,  though 
never  seen  projecting  from  the  genital  chamber,  is  evidently  protrac- 
tile, since  it  is  provided  with  a  long  basal  apodeme  (p)  on  which 
muscles  are  inserted.  The  apodeme  forks  in  the  wall  of  the  pouch, 
giving  one  branch  to  the  base  of  the  phallomere  arm,  and  sending  the 
other  through  the  mesal  wall  of  the  pouch  to  an  external  sclerite  above 
the  base  of  the  penis  (Pen).  On  the  inner  wall  of  the  pouch  is  a 
thick  rounded  fold  (/)  with  a  heavy,  dark,  crescentic,  marginal  sclero- 
tization.  The  retracted  penis  appears  as  a  conical,  membranous  lobe 
or  fold  (A,  C,  E,  Pen)  projecting  from  between  the  phallomere 
pouches,  and  bearing  at  its  apex  a  free  spine,  or  virga  (Vir).  Ventral 
to  the  base  of  the  virga  is  an  irregular  opening,  the  phallotreme, 
leading  into  a  large  endophallic  sac  (Enph),  which  receives  the 
ejaculatory  duct  (Dej)  near  its  anterior  end.  The  endophaUic  sac  of 
Blattella  apparently  is  equivalent  to  the  terminal  part  of  the  genital 
exit  passage  of  Periplaneta  and  Blatta  (fig.  14  B,  Enph)  opening  in 
the  membranous  fold  on  the  dorsal  side  of  the  base  of  the  ventral 
phallomere.  The  phallotreme  of  Blattella  is  on  the  ventral  surface  of 
the  penis,  which  fact  would  make  it  seem  improbable  that  the  penis 
represents  the  ventral  phallomere  of  the  Blattinae.  From  the  base  of 
the  virga  a  long  slender  apodeme  runs  forward  through  the  dorsal 
wall  of  the  endophallus  and  projects  anteriorly  as  a  free  rod  (fig.  16  A, 
C,  E,  Ape),  on  which  protractor  muscles  (E,  mcls)  are  inserted. 
In  a  young  male  nymph  of  Blattella  gennanica  the  ninth  abdominal 
sternum  is  a  simple,  symmetrical,  narrow  plate  (fig.  17  D,  IXS), 
bearing  two  widely  separated  styli  {Sty).  At  a  later  stage  (E)  it  is 
larger  and  produced  posteriorly  in  a  truncate  extension  on  which  the 
styli  are  closer  together,  but  it  still  shows  none  of  the  irregular 
features  of  the  adult  subgenital  plate  (A).  At  this  stage  the  phallic 
structures  are  distinct  lobes  (F)  arising  from  the  anterior  wall  of  the 
genital  chamber  above  the  ninth  sternum.  The  left  lobe  (IPJini) 
unquestionably  represents  the  left  phallomere  of  the  adult  because  in 
the  premoulting  period  a  hooked  structure  (G)  may  be  found  within 
it,  which  is  clearly  the  beginning  of  the  mature  form  of  the  organ  (H). 
The  right  phallomere  is  a  small  simple  lobe  (rPhiii)  on  the  right. 
Between  the  two  phallomere  lobes' is  a  sclerotic  point  (Vir),  which  is 
