NO.    5      MALE  GENITALIA  OF  ORTHOPTEROID  INSECTS SNODGRASS        4I 
are  dextral  in  position.  In  Blatta  and  Periplaneta  the  seminal  vesicles 
consist  of  two  groups  of  small  pyriform  sacs,  six  or  seven  on  each 
side,  arising  from  the  ventral  surface  of  the  ejaculatory  duct  at  the 
base  of  the  area  of  the  small  median  gland  tubules  (fig.  15  E,  Vsiii). 
The  vesicles  are  distinguishable  from  the  smaller  glands  by  their 
slightly  larger  size  and  more  opaque  whiteness ;  they  are  clearly  shown 
in  Blattahy  Miall  and  Denny  (1886,  fig.  99,  i),  who  did  not  recognize 
their  function.  The  sacs  are  filled  with  spermatozoa,  which  must  be 
stored  in  them  by  the  time  the  testes  go  into  a  state  of  degeneration. 
The  spermatozoa  of  Blattidae  are  very  small  as  compared  with  those 
of  Mantidae,  and  are  not  attached  to  one  another  in  bundles. 
TJie  pJiallic  gland. — A  large  gland  of  unknown  function,  the  "  con- 
globate gland  "  of  Miall  and  Denny,  or  "  prostate  gland  "  of  some 
other  writers,  is  associated  with  the  external  genital  organs  of  male 
Blattidae.  It  lies  beneath  the  accessory  glands  and  ejaculatory  duct, 
and  opens  on  the  phallic  region.  The  phallic  gland  of  Blatta  orientalis 
is  an  elongate  sac  (fig.  ii  C,  PhGld)  tapering  posteriorly  into  the  base 
of  the  left  phallomere  (fig.  14  A),  where  it  terminates  in  a  duct  that 
opens  on  a  membranous  space  between  the  two  middle  distal  lobes 
{r,  s)  of  the  appendage.  Ito  (1924)  mistakenly  says  that  the  duct 
of  the  gland  opens  into  the  posterior  extremity  of  the  ejaculatory 
duct.  The  phallic  gland  of  Periplaneta  aniericana  is  similar  to  that  of 
Blatta  except  that  it  is  subdivided  into  several  compact  lobes.  In 
Blattella  gernmnica  the  phallic  gland  consists  of  a  mass  of  coiled 
tubules  (fig.  16  B)  ;  its  long  slender  duct  opens  on  the  phallic  integu- 
ment mesad  of  the  mouth  of  the  sac  containing  the  left  phallomere 
(E,^). 
The  phallic  organs. — The  external  genital  apparatus  of  male 
roaches,  as  of  the  mantids,  consists  of  genital  lobes,  or  phallomeres, 
associated  with  the  mouth  of  the  ejaculatory  duct,  which  do  not  unite 
to  form  a  single  phallic  organ  comparable  with  that  of  other  Orthop- 
tera.  Two  distinct  types  of  phallic  structure  are  found  in  the  Blattidae ; 
one  is  characteristic  of  the  Blattinae;  the  other,  judging  from  various 
published  accounts,  but  principally  from  Chopard's  (1920)  compara- 
tive study  of  the  blattid  genitalia,  would  appear  to  occur,  with  various 
modifications,  in  most  of  the  other  subfamilies.  Presumably  inter- 
mediate forms  are  to  be  found  between  the  two  types,  but  it  is  not 
necessary  to  suppose  that  one  has  been  derived  from  the  other,  since 
both  types  have  a  similar  origin  in  nymphal  instars.  The  descriptions 
of  two  representative  species  of  each  type  here  given  can  serve  only 
as  a  basis  for  a  more  extensive  study,  which  might  lead  to  a  better 
understanding;  of  the  natural  classification  of  the  blattid  subfamilies. 
