326 DOMESTICATED TROUT. 



39. Examine mycropyle of egg. 



40. Examine germ of egg. 



41. Examine shell of egg. 



42. Examine freshly taken eggs while absorbing milt. 



43. Examine freshly taken eggs while germ is setting, i. e. 

 while stuck together in process of impregnation. 



44. Examine eggs while separating. 



Experiments with Alevins and Young Fry. 



45. See how long five alevins will live in a gill of water 

 at 36, at 42, at 50, at 60, at 70. 



46. Freeze alevins solid, thaw out, and return to the 

 water in hatching box, and watch for a month. Mem. : 

 Take care, during the freezing, not to disturb the fish, as it 

 will tear itself against the forming ice, and die from the ef- 

 fect of the laceration. The best way to freeze eggs or 

 young fish is to take a dry glass tumbler which has been 

 exposed to a great degree of cold, and pour into it the 

 specimens to be experimented with, together with about a 

 spoonful of water. The water, with the specimens, will 

 immediately freeze solid. 



47. Expose alevins to a rising temperature, and note 

 what degree of heat they will survive. 



Experiments with Young Fry. 



48-50. Repeat with trout fry the experiments with 

 alevins marked 26, 27, and 28. 



51. Keep very young trout fry in pure filtered spring 

 water, and note how long they remain healthy without the 

 addition of earth. 



52. After the fish in the last experiment begin to sicken, 

 apply earth plentifully, and note the improvement. 



53. Keep 100 young fry in a small box, and 100 in a 

 pond, for six months ; compare the mortality and growth. 



