It  may  be  agreed  that  since  differences  in  size  are  probably
affected  by  the  influences  of  life  and,  death  to  a  considerable
extent,  and  perhaps  unequally  eliminated  in  the  two  sexes,  they
do  not  form  a  reliable  guide  to  the  sexual  incidence  of  varia-
tions. But,  it  may  be  argued,  this  cannot  affect  measurements
made  at  birth,  and  we  must  therefore  accept  the  validity  of
those  of  Professor  Pearson's  measurements  which  concern  the
infant  at  birth.  Here,  however,  we  encounter  a  fact  which  is  of
the  first  importance  in  its  bearing  on  our  subject :  the  elimina-
tion of  variations  in  size  has  already  begun  at  birth,  and  there
is  reason  to  suppose  that  that  elimination  unequally  affects
males  and  females.  This  was  duly  allowed  for  in  Man  affd
Woman,  but  there  is  no  hint  of  it  throughout  Professor  Pearson's
long  paper.  He  does  not  dispute  this  influence,  nor  does  he
realise  that  until  he  has  disputed  it  his  conclusions  cannot  be
brought  to  bear  against  mine.  Professor  Pearson's  earlier
statistical  excursions  into  the  biological  field  were  chiefly  con-
cerned with  crabs  ;  in  passing  from  crabs  to  human  beings  he
failed  to  allow  for  the  fact  that  human  beings  do  not  come  into
the  world  under  the  same  conditions.  This  failure — pardonable
as  it  is  in  one  not  at  home  in  the  obstetrical  field — has  profoundly
affected  the  validity  of  his  cherished  criterion  of  sex  variability,
in  so  far  as  it  is  used  against  his  predecessors.
