﻿SPERMATOZOA. 
  75 
  

  

  X. 
  Spermatozoa. 
  

  

  The 
  seminal 
  elements 
  of 
  tailless 
  Batrachians 
  have 
  

   received 
  a 
  great 
  share 
  of 
  attention, 
  not 
  only 
  on 
  the 
  

   part 
  of 
  anatomists 
  and 
  physiologists, 
  but 
  even 
  of 
  

   systematic 
  workers. 
  This 
  is 
  due 
  to 
  the 
  great 
  amount 
  

   of 
  difference 
  in 
  structure 
  and 
  size 
  between 
  these 
  

   elements 
  in 
  the 
  various 
  genera; 
  and 
  also 
  to 
  the 
  fact 
  

   that 
  otherwise 
  closely 
  allied 
  species 
  of 
  the 
  genus 
  Bana 
  

   may 
  differ 
  in 
  their 
  spermatozoa 
  more 
  considerably 
  

   from 
  each 
  other 
  than 
  from 
  others 
  morphologically 
  

   more 
  remote. 
  The 
  failure 
  to 
  obtain 
  hybrids 
  between 
  

   such 
  near 
  allies 
  as 
  the 
  male 
  Bana 
  teivjjoraria 
  and 
  the 
  

   female 
  B. 
  arvalis 
  has 
  been 
  attributed 
  principally 
  to 
  

   these 
  differences; 
  for 
  other 
  species 
  of 
  the 
  genus 
  5^//o, 
  

   which 
  stand 
  very 
  far 
  apart, 
  but 
  which 
  have 
  almost 
  

   identical 
  spermatozoa 
  — 
  as, 
  for 
  instance, 
  B. 
  vulgaris 
  and 
  

   B. 
  calamita, 
  and 
  B. 
  vulgaris 
  and 
  B. 
  viridis 
  — 
  cross 
  with 
  

   comparative 
  facility 
  under 
  artificial 
  fecundation. 
  

  

  One 
  great 
  source 
  of 
  errors 
  in 
  describing 
  and 
  com- 
  

   paring 
  the 
  spermatozoa 
  has 
  been 
  due 
  to 
  the 
  changes 
  

   which 
  these 
  elements 
  undergo 
  in 
  their 
  development, 
  

   and 
  care 
  should 
  be 
  taken 
  to 
  ascertain 
  whether 
  or 
  not 
  

   they 
  are 
  in 
  a 
  ripe 
  condition. 
  The 
  safest 
  way 
  to 
  avoid 
  

   mistakes 
  is 
  not 
  to 
  extract 
  the 
  spermatozoa 
  from 
  the 
  

   testicles, 
  but 
  to 
  collect 
  them 
  in 
  the 
  seminal 
  ducts 
  

   from 
  specimens 
  in 
  embrace. 
  This 
  is, 
  however, 
  difficult 
  

   to 
  do 
  in 
  spexjies 
  which 
  are 
  destitute 
  of 
  a 
  seminal 
  

   bladder. 
  

  

  Thanks 
  to 
  the 
  investigations 
  of 
  Leydig, 
  La 
  Valette 
  

   St. 
  George, 
  Spengel, 
  and 
  Pfliiger, 
  which 
  I 
  have 
  been 
  

   able 
  to 
  supplement 
  for 
  some 
  of 
  the 
  less 
  known 
  species 
  

   of 
  Bana, 
  we 
  are 
  now 
  well 
  acquainted 
  with 
  the 
  sperma- 
  

   tozoa 
  of 
  nearly 
  all 
  the 
  European 
  species. 
  

  

  Those 
  of 
  Discoglossus 
  are 
  remarkable 
  for 
  their 
  great 
  

   size, 
  measuring 
  three 
  millimetres, 
  whilst 
  those 
  of 
  other 
  

   species 
  do 
  not 
  exceed 
  one-tenth 
  of 
  a 
  millimetre. 
  The 
  

   so-called 
  head 
  is 
  spirally 
  wound 
  like 
  a 
  corkscrew 
  ; 
  the 
  

  

  