118 MARVELS OF FISH LIFE 
as before the fillets were removed, and the relative 
position of the bones of the body, the head and fins 
remains the same. If all the skeletons which have been 
thrown aside are gathered at the end of the day, it will 
be found that they can be divided into groups of certain 
sizes. In the month of May, I found that the plaice 
in my fishmonger’s shop, with very few exceptions, 
could be divided into three groups, namely, a group of 
fish from fourteen to fifteen inches in length, another of 
about eighteen inches, and lastly, of fish from twenty 
to twenty-one inches. I took twelve fish from each of 
these groups and by examining the otoliths could read 
quite clearly that these plaice were respectively five, 
six and seven years old. I have never seen otoliths 
scientifically removed, but it is a very easy matter to 
get out the right and left otoliths in a few minutes from 
a number of plaice. 
Put the plaice on a board on its left or colourless 
side. Take the fishmonger’s largest knife and lay the 
edge of it along a line from the upper margin of the 
pectoral fin to a point an eye’s breadth above the upper 
eye; then strike the back of the knife a sharp blow with 
a mallet and cut right through the head. 
You will find that you have opened up a hollow 
space in the skull which is the front part of the cranial 
cavity. The back part of this cavity still has a dome- 
shaped covering of soft bone over it. Slip the point of 
a smaller knife under this dome-shape covering and cut 
directly upwards. Then pull open this back part of 
