﻿4 
  BRITISH 
  LEPIDOPTERA. 
  

  

  p. 
  387) 
  Antliroceraftlipendulae 
  paired 
  with 
  a 
  Procris. 
  Pairings 
  that 
  have 
  

   been 
  effected 
  in 
  confinement, 
  even 
  if 
  the 
  eggs 
  have 
  proved 
  infertile, 
  

   will 
  be 
  dealt 
  with 
  in 
  connection 
  with 
  our 
  notes 
  on 
  the 
  various 
  super- 
  

   families. 
  

  

  It 
  would 
  appear 
  that, 
  in 
  confinement, 
  closely 
  allied 
  species 
  belong- 
  

   ing 
  to 
  certain 
  groups 
  pair 
  more 
  readily 
  than 
  those 
  belonging 
  to 
  

   others, 
  and 
  the 
  production 
  of 
  hybrid 
  progeny 
  from 
  such 
  has 
  been 
  

   frequently 
  recorded. 
  To 
  what 
  extent 
  actual 
  alliance 
  between 
  the 
  

   parents 
  is 
  required 
  to 
  produce 
  fertile 
  ova, 
  and 
  subsequent 
  progeny, 
  

   is 
  not 
  known, 
  but 
  hybrid 
  progeny 
  has 
  thus 
  far 
  only 
  been 
  produced 
  

   between 
  quite 
  closely 
  allied 
  species 
  ; 
  the 
  most 
  distant 
  that 
  have 
  

   produced 
  fertile 
  eggs 
  and 
  subsequent 
  larva? 
  (which, 
  however, 
  did 
  

   not 
  produce 
  imagines), 
  appear 
  to 
  be 
  Saturnia 
  pa 
  von 
  i 
  a 
  $ 
  x 
  GraelUia 
  

   isabellae 
  ? 
  . 
  Pairings 
  like 
  that 
  of 
  Attacus 
  (Platyaamia) 
  cecropia 
  $ 
  

   X 
  Sphinx 
  ligustri 
  9 
  (Entom., 
  xix., 
  p. 
  136) 
  are 
  foredoomed 
  to 
  failure. 
  

   It 
  may 
  be 
  well 
  to 
  note 
  here 
  that 
  the 
  question 
  of 
  infertility 
  (which 
  

   Darwin 
  calls 
  sterility) 
  between 
  two 
  distinct 
  species 
  when 
  first 
  crossed, 
  

   appears 
  to 
  us 
  to 
  belong 
  to 
  an 
  entirely 
  different 
  class 
  of 
  biological 
  

   phenomena 
  from 
  the 
  sterility 
  of 
  hybrids, 
  the 
  product 
  of 
  such 
  a 
  cross. 
  

  

  We 
  may 
  assume 
  as 
  a 
  fact, 
  that 
  the 
  organs 
  of 
  reproduction 
  (external 
  

   and 
  internal) 
  of 
  any 
  two 
  pure 
  species 
  with 
  which 
  a 
  cross 
  is 
  attempted, 
  

   are 
  normally 
  perfect 
  anatomically 
  and 
  functionally, 
  and 
  that 
  the 
  

   female 
  is 
  primarily 
  capable 
  of 
  laying 
  her 
  normal 
  number 
  of 
  eggs. 
  

   That 
  she 
  should 
  not 
  lay 
  her 
  normal 
  number 
  of 
  eggs 
  if 
  the 
  $ 
  of 
  another 
  

   species 
  pair 
  with 
  her, 
  suggests 
  that 
  such 
  pairing 
  has 
  adversely 
  affected 
  

   her 
  ability 
  to 
  lay 
  all 
  the 
  eggs 
  that 
  she 
  otherwise 
  would 
  have 
  laid. 
  

   There 
  is 
  some 
  evidence 
  tending 
  to 
  suggest 
  that 
  certain 
  ? 
  s 
  have 
  had 
  

   their 
  egg-laying 
  power 
  decreased 
  by 
  cross-pairing, 
  although 
  most 
  lay 
  

   their 
  ordinary 
  quantum 
  of 
  eggs. 
  Again, 
  capable 
  as 
  the 
  eggs 
  are 
  of 
  

   being 
  fertilised 
  given 
  suitable 
  spermatozoa, 
  and 
  capable 
  as 
  the 
  

   spermatozoa 
  may 
  be 
  of 
  fertilising 
  given 
  suitable 
  ova, 
  it 
  is 
  certain 
  

   that 
  the 
  eggs 
  laid 
  by 
  a 
  2 
  crossed 
  by 
  a 
  S 
  of 
  another 
  species, 
  are 
  

   frequently 
  wholly, 
  or 
  in 
  great 
  part, 
  infertile, 
  among 
  all 
  but 
  the 
  most 
  

   closely 
  allied 
  species. 
  It 
  is 
  advisable, 
  however, 
  not 
  to 
  too 
  hastily 
  

   assume 
  that 
  attempted 
  crossings 
  are 
  ineffectual, 
  and 
  the 
  experience 
  of 
  

   Standfuss 
  illustrates 
  the 
  difficulty 
  of 
  drawing 
  conclusions 
  from 
  an 
  

   insufficient 
  number 
  of 
  experiments 
  or 
  trials. 
  Reference 
  to 
  his 
  account 
  

   (Handbiich, 
  &c, 
  pp. 
  60-61) 
  of 
  the 
  crossing 
  of 
  Malacosoma 
  neustria 
  $ 
  

   X 
  franconica 
  $ 
  , 
  shows 
  that, 
  of 
  24 
  trials 
  made, 
  the 
  results 
  gave 
  every 
  

   transition 
  between 
  complete 
  absence 
  of 
  issue, 
  and 
  the 
  deposition 
  of 
  

   eggs 
  normal 
  in 
  numbers 
  and 
  in 
  fertility, 
  failure 
  being, 
  in 
  some 
  

   instances, 
  according 
  to 
  Standfuss, 
  plainly 
  due 
  to 
  inadaptability 
  of 
  the 
  

   genital 
  apparatus." 
  Again, 
  in 
  1894, 
  Caradja 
  obtained 
  six 
  crossings 
  of 
  

   Spilosoma 
  mendica 
  $ 
  x 
  luctuosa 
  2 
  ; 
  all 
  the 
  2 
  s 
  laid 
  good 
  batches 
  

   of 
  eggs, 
  but 
  whilst 
  five 
  of 
  them 
  were 
  infertile, 
  the 
  sixth, 
  consisting 
  of 
  

   335 
  eggs, 
  produced 
  141 
  larvae 
  (the 
  eggs 
  first 
  laid 
  being 
  those 
  "that 
  

   hatched). 
  Chapman, 
  too, 
  obtained 
  (Ent. 
  Bee, 
  ii., 
  p. 
  83) 
  readily 
  

   enough 
  at 
  the 
  first 
  trial, 
  fertile 
  eggs 
  of 
  Amphidasys 
  strataria 
  x 
  betularia, 
  

   yet 
  all 
  his 
  later 
  attempts 
  failed. 
  Similarly, 
  in 
  the 
  Tephrosiid 
  hybrids 
  

   (Trans. 
  Ent. 
  Soc. 
  Lond,, 
  pp. 
  17-42) 
  it 
  was 
  found 
  that 
  the 
  intercrossings 
  

  

  * 
  This 
  explanation, 
  considering 
  that 
  some 
  pairings 
  produced 
  the 
  normal 
  

   number 
  of 
  fertile 
  eggs, 
  clearly 
  involves 
  the 
  assumption 
  of 
  considerable 
  variation 
  in 
  

   the 
  genital 
  apparatus, 
  of 
  which, 
  however, 
  Standfuss 
  gives 
  no 
  evidence. 
  

  

  