STOCKING THE CLYDE WITH GKEYLING. 295 



transparent that it is difficult to decide. The markings of 

 the vertebrse are apparent. The place of the vent is 

 indicated by a scarlet spot. 



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

 motion ; the yolk-sac much lessened in size. 



" 'Alst day, — The young fish are now perfect, and are 

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

 sac is absorbed. 



" ' These ova were daily examined by being placed 

 under the microscope or other magnifier, and part con- 

 tinually 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 rill falling into the Clyde, Hhs first fish 

 appeared on the seventeenth day, and the average was 

 twenty days. In some ova placed in boxes through 

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



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

 minnows, healthy, and in the evening ];ose 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 6^), and were doing well.' " 



