﻿[55] 
  DEVELOPMENT 
  OF 
  THE 
  CETACEA. 
  481 
  

  

  In 
  an 
  advanced 
  foetus 
  of 
  Phoccena 
  communis, 
  in 
  the 
  museum 
  col- 
  

   lections, 
  there 
  are 
  present 
  on 
  either 
  side 
  of 
  the 
  snout 
  two 
  strongly 
  de- 
  

   veloped 
  vibrissas 
  in 
  the 
  situation 
  corresponding 
  to 
  the 
  position 
  of 
  the 
  

   vibrissal 
  pits 
  or 
  follicles 
  noticed 
  in 
  a 
  much 
  younger 
  specimen, 
  in 
  which 
  

   these 
  are, 
  however, 
  much 
  more 
  numerous. 
  This 
  advanced 
  stage 
  was 
  

   kindly 
  brought 
  to 
  my 
  notice 
  by 
  Mr. 
  True. 
  Bschricht, 
  however, 
  calls 
  at- 
  

   tention 
  in 
  his 
  Untersuch. 
  uber 
  nordischen 
  Wallthiere 
  to 
  a 
  number 
  of 
  the 
  

   earlier 
  allusions 
  to 
  the 
  occurrence 
  of 
  such 
  hairs 
  on 
  young 
  cetaceans, 
  

   figuring 
  the 
  distribution 
  of 
  the 
  follicles 
  which 
  give 
  rise 
  to 
  them, 
  espe- 
  

   cially 
  those 
  seen 
  on 
  the 
  snout 
  of 
  the 
  foetus 
  of 
  Megaptera 
  longimana, 
  

   Fig. 
  16, 
  Plate 
  II, 
  between 
  the 
  blowholes 
  and 
  the 
  end 
  of 
  the 
  muzzle, 
  

   where 
  a 
  considerable 
  number 
  of 
  dermal 
  follicles 
  are 
  shown 
  as 
  elevations 
  

   of 
  the 
  integument, 
  though 
  they 
  do 
  not 
  show 
  much 
  greater 
  regularity 
  

   of 
  arrangement 
  in 
  rows 
  than 
  do 
  those 
  of 
  Bhachianectes. 
  Eschricht 
  also 
  

   figures 
  their 
  follicles 
  in 
  a 
  fcetus 
  of 
  Balcenoptera 
  rostrata, 
  Figs. 
  18 
  and 
  

   19, 
  Plate 
  III, 
  where 
  three 
  are 
  shown 
  above 
  the 
  margin 
  of 
  the 
  upper 
  lip, 
  

   and 
  four 
  on 
  the 
  lower, 
  the 
  upper 
  series 
  being 
  arranged 
  more 
  like 
  the 
  

   seven 
  shown 
  on 
  the 
  upper 
  lip 
  in 
  Fig. 
  5, 
  Plate 
  I, 
  or 
  in 
  a 
  single 
  row, 
  

   yet 
  it 
  appears 
  in 
  this 
  last 
  case, 
  after 
  comparison 
  of 
  this 
  stage 
  with 
  

   later 
  ones 
  of 
  the 
  same 
  species, 
  that 
  only 
  two 
  of 
  the 
  follicles 
  develop 
  

   outwardly 
  apparent 
  bristles, 
  five 
  of 
  them 
  subsequently 
  aborting 
  when 
  

   the 
  young 
  animal 
  is 
  about 
  a 
  foot 
  in 
  length. 
  Between 
  this 
  last-mentioned 
  

   stage 
  and 
  the 
  adult 
  condition 
  the 
  two 
  remaining 
  vibrissae 
  seem 
  to 
  disap- 
  

   pear 
  so 
  that 
  in 
  the 
  adult 
  Phoccena 
  no 
  vibrissas 
  are 
  distinguishable. 
  

  

  Inia, 
  with 
  its 
  feebly 
  developed 
  dorsal 
  fin 
  we 
  have 
  already 
  had 
  occasion 
  

   to 
  notice 
  as 
  less 
  specialized 
  in 
  that 
  respect 
  than 
  other 
  forms, 
  has 
  the 
  

   beak 
  provided 
  over 
  both 
  its 
  mandibular 
  and 
  maxillary 
  halves 
  with 
  

   short 
  bristles, 
  apparently 
  indicating 
  that 
  in 
  this 
  form 
  there 
  has 
  been 
  a 
  

   less 
  marked 
  loss 
  of 
  what 
  were 
  once, 
  in 
  part 
  at 
  least, 
  vibrissae, 
  such 
  as 
  

   are 
  found 
  over 
  the 
  upper 
  lip 
  of 
  fissipeds 
  and 
  pinnipeds, 
  and 
  below 
  the 
  

   mouth 
  and 
  above 
  it 
  in 
  Dicotyles. 
  

  

  The 
  strong 
  short 
  vibrissae 
  of 
  the 
  walrus 
  on 
  the 
  sides 
  of 
  the 
  muzzle 
  

   and 
  the 
  vibrissae 
  found 
  within 
  the 
  inflected 
  margins 
  of 
  the 
  lips 
  of 
  the 
  

   Manatee 
  are 
  somewhat 
  similar, 
  but 
  it 
  is 
  very 
  possible 
  that 
  the 
  protractile 
  

   and 
  retractile 
  lips 
  of 
  the 
  latter 
  animal 
  enables 
  it 
  to 
  use 
  these 
  stiff 
  bristles 
  

   as 
  prehensile 
  organs, 
  and 
  in 
  part 
  as 
  substitutes 
  for 
  incisors 
  in 
  grasping 
  

   and 
  tearing 
  off 
  the 
  soft 
  aquatic 
  or 
  marine 
  vegetation 
  upon 
  which 
  it 
  

   feeds. 
  

  

  The 
  distribution 
  of 
  the 
  vibrissae 
  on 
  the 
  snout 
  in 
  carnivorous 
  types 
  

   seems 
  to 
  be 
  mainly 
  over 
  the 
  sides 
  of 
  the 
  muzzle 
  above 
  the 
  mouth, 
  but 
  

   in 
  the 
  Ungulates, 
  especially 
  the 
  suilline 
  group, 
  vibrissae 
  are 
  found 
  

   both 
  above 
  and 
  below 
  the 
  mouth. 
  Inasmuch 
  as 
  the 
  whales 
  and 
  por- 
  

   poises 
  exhibit 
  both 
  of 
  these 
  distributions 
  of 
  their 
  vibrissae, 
  it 
  is 
  impos- 
  

   sible 
  to 
  draw 
  any 
  conclusions 
  from 
  their 
  mode 
  of 
  arrangement 
  which 
  

   will 
  be 
  of 
  any 
  value 
  in 
  determining 
  their 
  taxonomic 
  relations. 
  The 
  

   most 
  that 
  can 
  be 
  said 
  is 
  that 
  the 
  Balaenoid 
  cetaceans 
  seem 
  to 
  approxi- 
  

   S, 
  Mis. 
  70— 
  —31 
  

  

  