SHORES OF THE CLYDE AND FIRTH. 
27 
squares of wattles or wicker work, say a quarter of a mile 
each way. The top line, or, in other words, that portion 
of the square looking up the river, in each case should be 
left open to allow the down current of the river an easy flow 
through, and a number of diagonal lines, as shown (p. 26), 
should be placed in the interior for the purpose of inter- 
cepting the spat or spawn, and giving the young a better 
chance upon the bottom^ and a ready hold upon the 
wattles to mature. The squares could be placed at 
intervals, and set down and taken up at various times, so 
that a matured stock could always be found on the ground. 
From such a system I believe that the crops could be 
easily doubled annually, and although a small royalty was 
enforced from fishers, the country in the end would be 
much more benefited. A fresh water species of the 
mussel is to be found in several rivers in Scotland, notably 
the Clyde, and the Earn in Perthshire, being much sought 
after for the pearl the shell is sometimes found to contain. 
CHAPTER III. 
THE MYTILIS MODIOLUS. 
AT the lower ebb reaches of our shores another branch 
of the mussel family is frequently to be met with, 
viz., the mytilis modiolus, as it is classically called, and 
though not so numerous, nevertheless, in comparison to the 
common mussel, it attains a very large size, measuring 
