GROWTH AND NESTS OF FISHES. 613 



the ovum on February 26th, that is, forty-eight days after being 

 deposited ; and on April 8 th, or ninety days after impregnation of 

 the ova, the young were excluded. They measured -|ths of an 

 inch in length; the vitellicle being fths of an inch in length, 

 oblong in form, and of a light red colour : the tail was margined 

 like that of the tadpole, with a continuous fin running from the 

 dorsal above to the anal beneath. The vitelline sac and its con- 

 tents were absorbed by May 30th, or in about fifty days, until 

 which time the young fish did not leave the gravel of the hatch- 

 ing-pond. This quiescent state in their place of concealment, from 

 the period of exclusion to the absorption of the yolk, seems to 

 be common to Osseous Fishes ; but the time varies in different 

 species : it is much shorter in the Tench, Perch, or Pike, for 

 example, than in the Salmon. When the young Salmon mea- 

 sures an inch in length, the vertical fin begins to divide itself into 

 the dorsal, adipose, caudal and anal fins ; and the transverse bars 

 on the sides of the body make their appearance. It is very active, 

 and continues in the shallows of its native stream till the fol- 

 lowing spring, when it has attained the length of from three to 

 four inches, and is called the l May -parr.' In this state the 

 e parr ' descend into deeper parts of the river, and are believed by 

 Mr. Shaw to remain there over the second winter. The weaker 

 ones do so, but the stronger fish proceed to the estuary at 

 once. In April, the caudal, pectoral, and dorsal fins assume a 

 dusky margin ; the lateral bars begin to be concealed by a silvery 

 pigment ; and the migratory dress, characteristic of the stage 

 called ' smolt,' is assumed. Such fish begin in April and May 

 to congregate in shoals and to migrate seaward : they return in 

 July and August, of a size proportionate to the length of 

 their stay in the estuary. A smolt may not exceed two ounces 

 # in weight when it goes to sea: after a few months there it may 

 have grown to a ' grilse ' of eight or ten pounds' weight : ' at 

 two years and eight months old it becomes a Salmon of from 

 twelve to fifteen pounds' weight.' l It may subsequently acquire 

 a bulk of forty pounds' weight, and upwards. 



In the Si/ngnatlius acus the sexes come together in the month 

 of April, and the ova pass from the female and are transferred 

 into the subcaudal pouch of the male, fig. 426, n, being fecundated 

 in transitu, and the valves of the pouch immediately close over 

 them. In the month of July the young, ib. o, o, are hatched and 

 quit the pouch ; but they follow their father, and return for shelter 



1 ccexxv. p. 120. Experiments on marked fish have proved this extraordinary 

 rate of growth, cccxxxiv. p. 57. 



