94 PRACTICAL TROUT CULTURE. 



thin homeopathic vial of water, and held between 

 the observer and the light. Bright sunlight should 

 be avoided, the best illumination being given by 

 the reflection of the sun's rays from a white cloud. 

 When first placed in the tray, the entire egg is 

 filled with a gelatinous substance, on which float 

 minute granules and oil globules. Turn the egg 

 as you will, and still they will rise to the top. No 

 trace of division between the yolk and white ap- 

 pears until the second day, when the granules and 

 globules will be found to have separated them- 

 selves into a minute drop in the center of the 

 egg, surrounded on all sides by a transparent, 

 colorless zone, in which it freely floats. About 

 the fifth day a small prominence will appear upon 

 the top of this yolk, which will increase in size 

 daily. About the twelfth day an indentation may 

 be observed in this protuberance, and an almost 

 imperceptible line will be seen running from it. 

 Daily with the naked eye, and hourly beneath 

 the microscope, this line will be seen to increase in 

 length and breadth. It is the chorda dor sails or 

 spinal cord, the rudiment of the nervous system 

 of the future fish. About the eighteenth day it 

 has extended around one-half the yolk, one end 

 destined to form the tail being pointed, while the 

 other, forming the head, is flattened and thick- 

 ened. On the twentieth day the eyes appear, aiid 



