﻿art. 
  17 
  NEW 
  LARVAL 
  NEMATODES 
  SCHWARTZ 
  5 
  

  

  tightly 
  coiled, 
  the 
  comparatively 
  large 
  number 
  of 
  coils 
  filling 
  the 
  

   cyst 
  completely, 
  whereas 
  Ascaris 
  incisa 
  assumes 
  the 
  shape 
  of 
  the 
  

   figure 
  6 
  or 
  8 
  within 
  the 
  cyst, 
  the 
  interior 
  of 
  the 
  latter 
  being 
  but 
  

   partially 
  tilled 
  by 
  the 
  parasite. 
  Ascaris 
  acomthwa 
  has 
  a 
  shape 
  more 
  

   or 
  less 
  resembling 
  the 
  figure 
  8, 
  and 
  only 
  partially 
  fills 
  the 
  cyst, 
  so 
  

   far 
  as 
  can 
  be 
  judged 
  from 
  Leuckart's 
  figure. 
  The 
  species 
  from 
  the 
  

   mole 
  described 
  in 
  this 
  paper 
  (Porrocaecum 
  americanum) 
  is 
  similar 
  

   in 
  size 
  to 
  Ascaris 
  incisa, 
  but 
  in 
  view 
  of 
  the 
  fact 
  that 
  the 
  latter 
  ap- 
  

   pears 
  to 
  be 
  a 
  group 
  name, 
  and 
  that 
  a 
  precise 
  account 
  of 
  its 
  morph- 
  

   ology 
  has 
  not 
  been 
  published, 
  it 
  is 
  more 
  desirablej 
  not 
  to 
  add 
  to 
  the 
  

   already 
  existing 
  confusion, 
  and 
  accordingly 
  the 
  form 
  from 
  the 
  

   American 
  mole 
  (Scalopus 
  aquaticus) 
  may 
  best 
  be 
  considered 
  dis- 
  

   tinct 
  from 
  that 
  from 
  the 
  European 
  mole 
  (Talpa 
  europaea). 
  

  

  THE 
  GENUS 
  PORROCAECUM 
  RAILLIET 
  AND 
  HENRY 
  1912 
  

  

  The 
  genus 
  Porrocaecum 
  is 
  included 
  in 
  the 
  family 
  Ascaridae, 
  and 
  

   according 
  to 
  a 
  recent 
  revision 
  of 
  this 
  family 
  by 
  Baylis 
  (1920), 
  it 
  is 
  

   assigned 
  to 
  the 
  subfamily 
  Anisikinae 
  Iiailliet 
  and 
  Henry, 
  1921, 
  

   emended 
  by 
  Baylis, 
  1920. 
  Baylis 
  defines 
  the 
  genus 
  Porrocaecum 
  as 
  

   follows 
  : 
  " 
  Esophagus 
  with 
  anterior 
  muscular 
  portion 
  and 
  posterior 
  

   ventriculus 
  of 
  oblong 
  shape, 
  the 
  latter 
  short 
  in 
  the 
  genotype, 
  but 
  

   in 
  other 
  species 
  frequently 
  long 
  and 
  bent 
  at 
  an 
  angle 
  so 
  as 
  to 
  open 
  

   into 
  the 
  intestine 
  laterally. 
  An 
  intestinal 
  cecum 
  present. 
  No 
  eso- 
  

   phageal 
  appendix. 
  Interlabia 
  present, 
  usually 
  small 
  dentigerous 
  

   ridges 
  present." 
  Fifteen 
  species 
  belonging 
  to 
  this 
  genus 
  are 
  listed 
  

   in 
  the 
  catalogue 
  of 
  the 
  Zoological 
  Division 
  of 
  the 
  Bureau 
  of 
  Animal 
  

   Industry, 
  the 
  hosts 
  being 
  fishes, 
  amphibia, 
  birds, 
  and 
  marine 
  mam- 
  

   mals. 
  At 
  least 
  one 
  species 
  (Porrocaecum 
  crassum) 
  is 
  probably 
  of 
  

   economic 
  importance, 
  since 
  it 
  occurs 
  in 
  ducks. 
  It 
  is 
  not 
  improbable 
  

   that 
  further 
  investigations 
  will 
  add 
  to 
  the 
  number 
  of 
  species 
  of 
  

   Porrocaecum 
  on 
  the 
  one 
  hand 
  and 
  subtract 
  from 
  it 
  on 
  the 
  other 
  

   hand. 
  Only 
  five 
  species 
  listed 
  under 
  this 
  genus 
  are 
  regarded 
  by 
  

   Baylis 
  (1920) 
  as 
  probably 
  belonging 
  to 
  it, 
  while 
  the 
  same 
  writer 
  

   regards 
  certain 
  species 
  from 
  fish 
  with 
  a 
  type 
  of 
  alimentary 
  canal 
  

   characteristic 
  of 
  the 
  genus, 
  but 
  not 
  as 
  yet 
  included 
  in 
  it, 
  as 
  requiring 
  

   further 
  investigation. 
  It 
  may 
  be 
  concluded, 
  therefore, 
  that 
  our 
  

   knowledge 
  of 
  the 
  genus 
  is 
  as 
  yet 
  incomplete, 
  and 
  that 
  further 
  investi- 
  

   gation 
  will 
  probably 
  result 
  in 
  bringing 
  to 
  light 
  additional 
  species 
  

   which 
  may 
  lead 
  to 
  a 
  new 
  conception 
  regarding 
  the 
  affinities 
  of 
  the 
  

   various 
  members 
  now 
  included 
  in 
  it. 
  

  

  % 
  LIFE 
  HISTORY 
  OF 
  SPECIES 
  OF 
  PORROCAECUM 
  

  

  Our 
  present 
  knowledge 
  of 
  the 
  life 
  history 
  of 
  species 
  of 
  Porro- 
  

   caecum 
  is 
  very 
  fragmentary, 
  the 
  essential 
  facts 
  being 
  understood 
  in 
  

   only 
  two 
  species, 
  so 
  far 
  as 
  the 
  present 
  writer 
  has 
  been 
  able 
  to 
  ascer* 
  

  

  