﻿art. 
  17 
  NKW 
  LARVAL 
  NEMATODES 
  SCHWARTZ 
  7 
  

  

  forms 
  described 
  by 
  the 
  present 
  writer 
  have 
  a 
  well-developed 
  intes- 
  

   tinal 
  cecum, 
  they 
  also 
  have 
  a 
  conspicuous 
  ventriculus, 
  and 
  are 
  there- 
  

   fore 
  probably 
  not 
  identical 
  with 
  Porrocaecum 
  reticulatum. 
  How- 
  

   ever, 
  as 
  already 
  stated 
  elsewhere 
  in 
  this 
  paper, 
  the 
  immaturity 
  of 
  

   the 
  present 
  writer's 
  specimens 
  does 
  not 
  warrant 
  comparison 
  with 
  

   any 
  known 
  adult 
  forms. 
  

  

  The 
  determination 
  of 
  the 
  adult 
  stages 
  of 
  Porrocaecum 
  encapsu- 
  

   latum 
  and 
  Porrocaecum 
  americanum 
  must 
  await 
  the 
  examination 
  of 
  

   probable 
  definite 
  bird 
  hosts 
  in 
  the 
  vicinity 
  of 
  the 
  District 
  of 
  Co- 
  

   lumbia 
  and 
  Virginia 
  for 
  parasites 
  of 
  the 
  digestive 
  tract, 
  and 
  the 
  

   experimental 
  infection 
  of 
  birds 
  with 
  Porrocaecum 
  as 
  a 
  result 
  of 
  

   feeding 
  them 
  encysted 
  larvae 
  from 
  intermediate 
  hosts. 
  

  

  SUMMARY 
  

  

  Two 
  encysted 
  larval 
  nematodes 
  occurring 
  in 
  Insectivora 
  are 
  de- 
  

   scribed 
  for 
  the 
  first 
  time 
  from 
  the 
  United 
  States, 
  and 
  are 
  definitely 
  

   shown 
  to 
  belong 
  to 
  the 
  genus 
  Porrocaecum. 
  These 
  forms 
  appear 
  to 
  

   be 
  related 
  to 
  encysted 
  nematodes 
  described 
  from 
  moles 
  and 
  shrews 
  

   in 
  Europe 
  under 
  the 
  name 
  Ascaris 
  incisa 
  and 
  under 
  other 
  names, 
  

   but 
  are 
  distinct 
  from 
  the 
  European 
  forms 
  as 
  regards 
  location 
  in 
  

   the 
  host 
  as 
  well 
  as 
  regards 
  certain 
  morphological 
  characters. 
  

   Porrocaecum, 
  encapsulatum 
  described 
  in 
  this 
  paper 
  from 
  the 
  shrew 
  

   (Blarina 
  brevicauda) 
  is 
  strikingly 
  larger 
  than 
  any 
  of 
  the 
  related 
  

   forms 
  heretofore 
  known, 
  and 
  Porrocaecum 
  americanum 
  from 
  the 
  

   mole 
  (Scalopus 
  aquations) 
  though 
  agreeing 
  in 
  size 
  with 
  Ascaris 
  

   incisa 
  is 
  considered 
  distinct, 
  because 
  the 
  latter 
  is 
  probably 
  a 
  group 
  

   name 
  and 
  has 
  been 
  incompletely 
  described, 
  so 
  that 
  there 
  exists 
  no 
  

   definite 
  basis 
  on 
  which 
  to 
  make 
  morphological 
  comparisons. 
  

  

  The 
  adult 
  forms 
  of 
  the 
  larvae 
  here 
  described 
  (Porrocaecum 
  encap- 
  

   sulatum, 
  and 
  Porrocaecum 
  americanum) 
  probably 
  occur 
  in 
  birds 
  of 
  

   pre}', 
  such 
  as 
  hawks 
  and 
  owls. 
  Owing 
  to 
  the 
  incomplete 
  state 
  of 
  

   development 
  of 
  these 
  larvae, 
  particularly 
  as 
  regards 
  the 
  mouth 
  parts, 
  

   it 
  is 
  impossible 
  to 
  compare 
  them 
  to 
  any 
  advantage 
  with 
  adult 
  speci- 
  

   mens 
  of 
  Porrocaecum 
  collected 
  from 
  American 
  birds 
  of 
  prey. 
  The 
  

   ultimate 
  solution 
  of 
  the 
  question 
  of 
  the 
  adult 
  stages 
  of 
  the 
  larvae 
  

   described 
  in 
  this 
  paper 
  will 
  have 
  to 
  be 
  based 
  on 
  more 
  complete 
  

   knowledge 
  of 
  the 
  species 
  of 
  Porrocaecum 
  that 
  occur 
  in 
  American 
  

   birds 
  of 
  prey 
  and 
  on 
  feeding 
  experiments. 
  

  

  REFERENCES 
  TO 
  LITERATURE 
  CITED 
  

   Bayus, 
  H. 
  A. 
  

  

  1920. 
  — 
  On 
  the 
  classification 
  of 
  the 
  Ascaridae. 
  1. 
  The 
  systematic 
  value 
  of 
  

   certain 
  characters 
  of 
  the 
  alimentary 
  canal, 
  Parasitology, 
  Cambridge 
  

   [Eng.], 
  vol. 
  12, 
  ser. 
  3, 
  Sept., 
  pp. 
  253-264, 
  figs. 
  1-6. 
  

   1924. 
  — 
  Some 
  considerations 
  on 
  the 
  host-distribution 
  of 
  parasitic 
  nema- 
  

   todes, 
  Linnean 
  Soc. 
  Journ.,-Zool., 
  vol. 
  36, 
  April, 
  pp. 
  13-23. 
  

  

  