NO.    5      MALE  GENITALIA  OF  ORTHOPTEROID  INSECTS — SNODGRASS  "] 
from  the  work  of  Heymons  and  of  Wheeler  on  Periplaneta,  Blattella, 
Grylliis,  and  Conocephalus,  and  recently  has  been  shown  to  occur  in 
Acrididae  by  Else  (1934)  and  by  Roonwal  (1937).  The  cavities  are 
present  in  the  ampullae  long  before  the  lumina  appear  in  the  other 
parts  of  the  ducts.  The  ampullar  cavities  are  ventral  remnants  of 
the  coelomic  sacs  of  the  tenth  abdominal  somite,  and  similar  though 
transient  ampullae  of  coelomic  origin  may  occur  in  the  preceding 
abdominal  somites.   To  the  ampullae  of  the  tenth  segment  of  the  male, 
VIII- 
IX''""  >(  -       — t^ 
xi-X  ~'^^'' 
Fig.  2. — Development  of  the  male  genital  ducts  and  accessory  glands  of 
Orthoptera.    (A,  B,  simplified  from  Wheeler,  1893;  C,  D,  diagrammatic.) 
A,  abdomen  of  embryo  of  Conocephalus  brevipennis  (Scudder)  with  vasa 
deferentia  ending  in  ampullae  contained  in  appendage  rudiments  of  tenth  abdomi- 
nal segment  (XApd).  B,  same,  later  stage,  ampullae  dislodged  from  appendages 
and  approximated  medially.  C,  diagram  of  usual  condition  of  genital  ducts  in 
an  orthopteran  nymph,  ampullae  (Amp)  united  with  each  other  and  with 
anterior  end  of  an  ectodermal  ductus  ejaculatorius  (Dej).  D,  diagram  of  typi- 
cal structure  of  internal  male  genitalia  of  adult  Orthoptera,  in  which  the  acces- 
sory glands  (AcGlds)  and  vesiculae  seminales  (Vsm)  are  outgrowths  of  the 
united  mesodermal  genital  ampullae  (Amp). 
AcGlds,  accessory  genital  glands ;  Amp.  coelomic  ampullae  of  genital  ducts ; 
Cer,  cercus;  Dej,  ductus  ejaculatorius;  Sty,  stylus  of  ninth  abdominal  segment; 
Tes,  testis ;  Vd,  vas  deferens ;  Vsm,  vesicula  seminalis :  VIII,  IX,  X,  eighth, 
ninth,  and  tenth  abdominal  segments ;  XApd,  appendage  rudiment  of  tenth 
abdominal  segment. 
however,  are  attached  the  posterior  ends  of  the  genital  strands  that 
become  the  vasa  deferentia  (fig.  2  A).  The  ampullae  persist,  first 
as  terminal  parts  of  the  lateral  ducts,  but  later  united  as  an  anterior 
part  of  the  definitive  median  ejaculatory  duct  (C,  D,  Amp). 
Inasmuch  as  the  gonadial  parts  of  the  embryonic  genital  ridges 
shorten  during  their  development,  with  a  complemental  lengthening 
of  the  parts  forming  the  ducts,  it  seems  very  probable  that  each 
entire  ridge  was  primarily  a  gonad,  and  that  the  terminal  ampullae 
alone  represent  the  primitive  coelomic  outlet  ducts.  If  this  is  true,  as 
the  occurrence  of  germ  cells  as  far  back  as  the  tenth  abdominal  somite 
