lO  SMITHSONIAN    MISCELLANEOUS    COLLECTIONS  VOL.    96 
It  should  be  observed  that  the  median  penis  as  formed  in  certain 
Ephemeroptera  and  some  Dermaptera  is  quite  a  different  structure 
from  the  median  penis,  or  phaUus,  of  Orthoptera,  because  it  is  clearly 
a  product  of  the  union  of  two  separate  penes  each  containing  an  out- 
let duct.  A  median  penis  of  this  type  the  writer  (1936)  has  desig- 
nated a  penis  conjunct  us;  it  frequently  recurs  in  Crustacea  and 
Diplopoda.  The  median  penis  of  Orthoptera,  and  probably  that  of 
most  pterygote  insects,  on  the  other  hand,  is  a  penis  communis,  since, 
however  formed,  it  is  not  produced  by  the  union  of  two  primary 
organs  containing  each  the  outlet  of  a  primitive  lateral  duct.  The 
definitive  median  duct,  or  ductus  ejaculatorius,  of  the  phallus  is  an 
independent  structure,  single  in  its  origin — it  is  a  ductus  cojnmunis, 
not  a  ductus  conjunctus,  nor  a  persistent  branch  of  conjoined  ducts 
as  in  some  Dermaptera. 
Since  in  some  cases  there  are  only  two  primitive  phallic  lobes  in 
the  nymph,  or  a  pair  of  lateral  lobes  take  a  predominant  part  in  the 
formation  of  the  adult  phallic  structure,  it  might  be  supposed  that 
these  lobes  are  derived  from  the  segmental  appendages  of  the  tenth 
abdominal  somite.  According  to  Wheeler  (1893)  the  embryonic  tenth 
appendage  rudiments  of  the  male  of  Conoccphalus,  after  the  ampullae 
have  withdrawn  from  them,  disappear.  It  is  claimed  by  Else  (1934), 
however,  that  the  appendage  rudiments  of  the  tenth  segment  in 
Melanoplus  persist  and  continue  their  migration  toward  the  median 
line  until  they  take  a  position  at  the  sides  of  the  point  where  the 
ejaculatory  duct  invagination  is  being  formed.  Here,  he  says,  they 
grow  out  into  lobes  that  unite  about  the  mouth  of  the  duct,  and 
eventually  form  the  complex  phallic  organ  of  the  adult,  which  con- 
tains the  gonopore. 
An  origin  of  the  acridid  phallus  from  appendage  rudiments  is 
described  also  by  Roonwal  (1937)  in  Locusta  migratoria,  but  Roon- 
wal  claims  that  the  appendages  both  of  the  tenth  and  the  ninth  seg- 
ments are  involved.  He  says:  "the  tenth  abdominal  appendages 
shift  forwards  and  fuse  with  the  ninth,  and  together  they  form  the 
aedeagus  and  its  duct  (ejaculatory  duct)  and  associated  structures." 
Inasmuch  as  the  ninth  segment  appendages  of  most  other  orthop- 
teroid  families  become  the  styli  of  the  definitive  ninth  sternum,  it 
seems  hardly  credible  that  they  should  take  part  in  the  formation  of 
the  phallus  in  an  acridid,  and,  as  above  noted,  the  appendage  rudi- 
ments of  the  ninth  segment  of  Melanoplus  are  said  by  Else  to  disap- 
pear. Otherwise,  the  accounts  of  the  development  of  the  acridid 
phallus  as  given  by  Else  and  by  Roonwal  are  in  essential  agreement. 
