252 APPENDIX. 



transparent that it is difficult to decide. Tlie markings of 

 tlie vertetrffi are apparent. The place of the vent is 

 indicated hy a scarlet spot. 



" ' 33rd day. — The mouth is now in constant but slow 

 motion ; the yolk-sac much lessened in size. 



" ' 41s< day. — The young fish are now perfect, and are 

 about nine-tenths of an inch ia length, and the umbilical 

 sac is absorbed. 



" ' These ova were daily examined by being placed 

 under the microscope or other magnifier, and part con- 

 tiQually destroyed, probably from the concentrated light 

 of the lenses. On one occasion Mr. Eyre and Mr. Peach 

 were examining a rather forward-looking ovum under the 

 microscope, when the fish, by an instantaneous effort, 

 burst the membrane or chorion, and in a few minutes 

 after they saw him, by another effort, free himself entirely 

 from it. This was a piece of wonderful good fortune, as 

 that particular operation might have been watched for for 

 years fruitlessly. 



" 'In the natural rOl falling into the Clyde, \h& first fish 

 appeared on the seventeenth day, and the average was 

 twenty days. In some ova placed in boxes through 

 which the same riU ran, the average time was forty days. 



"'In June, 1857, these fish were about the size of 

 minnows, healthy, and in the evening rose freely at small 

 flies. I estimated their number at 3,000 or 4,000. 



" ' In March 1858 they were on the average five inches 

 in length (some reached 6J), and were doing well.' " 



