﻿Reproductive 
  organs 
  of 
  Taenia 
  pisiformis. 
  409 
  

  

  occurs. 
  That 
  chromidia 
  are 
  thrown 
  off 
  during 
  early 
  stages 
  of 
  de- 
  

   velopment 
  is 
  undoubtedly 
  true, 
  but 
  for 
  reasons 
  already 
  stated, 
  I 
  

   cannot 
  interpret 
  them 
  as 
  polar 
  bodies. 
  The 
  other 
  type 
  of 
  cell, 
  

   which 
  has 
  been 
  interpreted 
  as 
  a 
  polar 
  body, 
  shows 
  similar 
  lack 
  of 
  

   evidence 
  to 
  support 
  such 
  a 
  view 
  ; 
  while 
  my 
  own 
  observations, 
  coupled 
  

   with 
  those 
  of 
  Leuckaet 
  (1856) 
  and 
  von 
  Janicki 
  (1907) 
  support 
  a 
  

   different 
  interpretation. 
  

  

  The 
  degeneration 
  of 
  gametogenesis, 
  as 
  well 
  as 
  that 
  of 
  ordinary 
  

   mitosis, 
  is 
  further 
  evidence 
  in 
  support 
  of 
  my 
  previously 
  published 
  

   view 
  (Young, 
  1908, 
  1910, 
  1912a) 
  that 
  the 
  cestode 
  nucleus 
  is 
  

   primarily 
  physiological 
  rather 
  than 
  morphological 
  in 
  character, 
  for 
  

   development 
  occurs 
  here 
  without 
  the 
  typically 
  precedent 
  processes 
  

   of 
  maturation. 
  A 
  conception 
  of 
  any 
  definite 
  morphological 
  elements 
  

   carrying 
  specific 
  maternal 
  and 
  paternal 
  characters 
  from 
  parent 
  to 
  

   offspring, 
  and 
  from 
  cell 
  to 
  cell, 
  or 
  of 
  chromosome 
  "individuality" 
  or 
  

   "genetic 
  continuity" 
  appears 
  to 
  me 
  untenable 
  here. 
  

  

  The 
  wide 
  departures 
  from 
  the 
  usual 
  developmental 
  and 
  cyto- 
  

   logical 
  processes 
  of 
  other 
  animals, 
  which 
  are 
  shown 
  by 
  cestodes, 
  do 
  

   not 
  however 
  authorize 
  us 
  to 
  draw 
  any 
  conclusions 
  regarding 
  these 
  pro- 
  

   cesses 
  in 
  general, 
  which 
  are 
  based 
  upon 
  such 
  aberrant 
  forms. 
  That 
  

   mitosis 
  and 
  the 
  chromosome, 
  maturation 
  and 
  fertilization 
  may 
  all 
  

   be 
  of 
  great 
  significance 
  in 
  the 
  heredity 
  and 
  development 
  of 
  most 
  

   organisms, 
  and 
  yet 
  have 
  lost 
  such 
  significance, 
  at 
  least 
  in 
  great 
  

   part, 
  in 
  these 
  degenerate 
  forms 
  is 
  by 
  no 
  means 
  impossible. 
  They 
  

   do 
  suggest 
  however, 
  that 
  norm.al 
  development 
  and 
  the 
  transmission 
  

   of 
  characters 
  are 
  not 
  necessarily 
  dependent 
  upon 
  these 
  processes 
  even 
  

   in 
  the 
  Metazoa; 
  and 
  should 
  put 
  us 
  on 
  our 
  guard 
  against 
  ascribing 
  

   too 
  much 
  influence 
  to 
  them 
  until 
  more 
  positive 
  evidence 
  of 
  their 
  

   function 
  is 
  obtained. 
  

  

  Summary. 
  

  

  In 
  Taenia 
  pisiformis 
  the 
  reproductive 
  organs 
  are 
  developed 
  prob- 
  

   ably 
  mainly 
  in 
  situ 
  from 
  the 
  parenchyma. 
  There 
  is 
  no 
  evidence 
  of 
  

   specificity 
  of 
  cells, 
  apparently 
  any 
  cell 
  may 
  partake 
  in 
  the 
  formation 
  

   of 
  any 
  organ. 
  

  

  An 
  epithelium 
  is 
  present 
  in 
  some 
  adult 
  organs; 
  absent 
  in 
  others, 
  

   being 
  here 
  directly 
  metamorphosed 
  to 
  form 
  a 
  cuticula. 
  

  

  Mitosis 
  seldom 
  occurs 
  save 
  in 
  later 
  cleavage 
  stages 
  and 
  in 
  an 
  

   abortive 
  condition 
  in 
  gametogenesis. 
  Evidence 
  of 
  its 
  degeneration 
  

  

  