CHOICE OF PATTERN 107 



genital glands. Large specimens, of course, differ in 

 the head, which is larger and hooked at the snout in 

 the males." 



My keeper is, as a rule, correct in his determination 

 of the sex from outward appearance. He relies 

 chiefly on the size and shape of the head, and also on 

 the shape of the gill-cover, which he says is more 

 pointed in the male and rounder in the female. If in 

 doubt he examines the vent, in which there are two 

 orifices or openings in the female (one the end of the 

 tube down which the eggs pass, and the other the end 

 of the excretory passage), while in the male there is 

 only one opening. 



On this point Mr. Boulenger is kind enough to 

 say : " Big males of Salmo fario are, of course, easy 

 to tell from females by the large head, but it is not so 

 in smaller specimens, and I doubt whether the shape 

 of the gill-cover would afford any help. As to the 

 pore behind the vent (the peritoneal pore), it is, as you 

 say, present in the female and absent in the male ; but 

 it is not always easy to see, so that I would not 

 recommend the character for the use of the non- 

 scientific." 



If trout are fished for during the second half of 

 September on the Test, fishermen should make it a 

 rule to return all female fish and kill only males. 

 The males in all streams and especially in those 

 which are much fished, largely outnumber the females, 

 so that we can well afford to kill males during Sep- 

 tember. The patterns for day, evening and night 



