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tely  imbricated,  there  is  always  and  constantly  to  find  placed  between 
every  two  scales  a  long  stiff  hair  flanked  by  the  two  short  hairs.  Where 
the  scales  are  black,  there  the  stiff  hairs  too  are  black,  where  the  for- 
mer are  yellow,  there  the  latter  too  are  yellow.  The  yellow  distal  part 
of  the  tail  measures  about  150  Mm.,  that  is  also  3/7  of  its  whole  length 
—  in  TJromys  macropus  the  tail  is  yellow  for  2/3  of  its  length. 
I  discussed  the  covering  of  the  tail  somewhat  in  extenso ,  because 
this  point  seems  nearly  always  to  have  been  overlooked  as  insignifi- 
cant, —  at  least  this  organ  has  been  always  described  as  being  more 
or  less  hairy  or  naked  *)  a.  s.  o.  —  and  more  especially  as  Professor  Max 
Weber  has  brought  this  matter  in  discussion;  see  his  paper  entitled 
„Beiträge  zur  Anatomie  und  Entwickelung  des  Genus  Manis"  in  „Zoo- 
logische Ergebnisse",  1891,  zweiter  Band,  Erstes  Heft. 
There  is  an  endless  variation  in  size  and  shape  of  the  scales  of  the 
tails  among  the  different  Mice- species,  as  well  as  in  the  form  of  their 
margin,  but  very  constant  seems  to  be  the  above  described  arrange- 
ment of  the  three  hairs  with  respect  to  the  scales.  The  mentioned 
hairs  may  be  shorter  or  longer,  so  that  the  tail  looks  more  or  less 
hairy,  probably2)  it  will  appear  that  this  does  not  depend  on  the 
number  of  the  hairs  which  (perhaps)  always  and  constantly  is  equal  to 
three  times  the  number  of  scales.  It  seems  to  me  that  I  detected  here 
a  highly  important  and  interesting  law  of  nature  of  a  very  far  rea- 
ching significance.  Horsfield  has  paid  more  attention  to  the  arrange- 
ment of  the  hairs  of  the  tail  than  all  later  authors  did  together,  at 
least  he  was  on  the  point  to  detect  the  above  explained  law,  as  he 
wrote  in  1824  (Zoological  researches  in  Java)  à  propos  Mus  setifer: 
„the  tail  is  more  naked  than  that  of  the  Mus  decumanus;  a  few  short 
„delicate  hairs  arise,  in  very  small  tufts  of  two  or  three,  3)  from  the 
„ scales  composing  the  rings." 
Above  I  remarked  that  in  M.  armandvillei  there  are  on  hands  and 
feet  short  stiff  hairs  placed  in  very  regular  parallel  rows;  well  then, 
although  true  scales  are  absent  the  underlying  tabulated  skin  is  very 
good  developed  and  here  again  the  hairs  generally  are  arranged  in 
distinctly  separate  groups  of  three,  rising  from  the  distal  margin  ol 
1)  As  far  as  I  am  aware  there  are  no  Mice  with  a  naked  tail. 
2)  I  say  „probably"  as  I  had  no  time  to  examine  all  the  different  species,  but  I  saw 
it  in  every  specimen  that  I  examined,  in  specimens  belonging  to  Hesperomys-species  too. 
3)  I  italicize. 
6 
