ZOOLOGY. 355 



vial matter deposited in time of flood will often bury the ova too deep to ad- 

 mit of the extrication of the young fry, even if hatched. The impetuosity of 

 the streams flooded will frequent^ sweep away whole spawning beds and 

 their contents. While deposited in boxes, the ova are protected from injury, 

 and their vivification in large numbers is thus rendered a matter of certainty, 

 and the young fish are reared in safety. On the 31st of March, 1854, the first 

 ovum was observed to be hatched, and in April and May the greater portion 

 had come to life, and were at large in the boxes ; in June they were admitted 

 into the pond, their average size being about an inch and a half in length. 

 From the period of their admission to the pond the fry were fed daily with 

 boiled liver, rubbed small by the hand. Xot withstanding the severity of the 

 winter, they continued in a healthy condition, and in the spring of the year 

 1855 were found to have increased in size to the average of three and four 

 inches in length. On the 2d of May, 1855, a meeting of the committee was 

 held at the pond, to consider the expediency of detaining the fry for another 

 year or allowing them to depart. A comparison with the undoubted smelts 

 of the river then descending seaward with the fry in the ponds, led to the 

 conclusion that the latter were not yet smelts, and ought to be detained. 

 Seventeen days afterward, viz., on the 19th of May, a second meeting was 

 held, in consequence of great numbers of the fry having in the interim as- 

 sumed the migratory dress. On inspection it was found that a considerable 

 portion were actual smelts, and the committee came to the determination to 

 allow them to depart. Accordingly the sluice communicating with the Tay 

 was opened, and every facility for egress afforded. Contrary to expectation, 

 none Qf the fry manifested any inclination to leave the pond until the 24th of 

 May, when the larger and more mature of the smelts, after having held them- 

 selves detached from the others for several days, went off in a body. A series 

 of similar emigrations took place until fully one half the fry had left the pond, 

 and descended the sluice to the Tay. It has long been a subject .of contro- 

 versy whether the salmon assume the migratory dress in the second or third 

 year of their existence. In order to test the matter in the fairest possible 

 way, it was resolved to mark a portion of the smelts in such a manner that 

 they might easily be detected when returning as grilse. A temporary tank, 

 into which the fish must necessarily descend, was constructed at the junction 

 of the sluice with the Tay ; and as the shoals successively left the pond, about 

 one in every hundred was marked by the abscission of the second dorsal fin. A 

 greater number were marked on the 29th of May than on any other day, in 

 all about 1,200 or 1.300. The result has proved highly satisfactory. Within 

 two months of the date of their liberation, namely, between May 29 and July 

 31, twenty-two of the young fish so marked when in the state of smelts 

 on their way to the sea, have been in their returning migration up the river, 

 recaptured and carefully examined ; the conclusions arrived at are most grati- 

 fying, and prove what has heretofore appeared almost incredible, namely, the 

 rapid growth of the young fish during their short sojourn in the salt water ; 

 this fact may be considered as still farther established by observing the in- 

 creased weight according to date of the grilse caught and examined ; those 

 taken first w eighing 5 to 5 Ibs., then increasing progressively to 7 and 8 Ibs. ; 



