221 
where it may be subjected to the action of the air and 
water, these worms are playing an important part in the 
removal of products, which, if left to accumulate, would 
scon become objectionable. 
The number of worms, and therefore of castings, 
varies considerably in different sands. Davison* has given 
an account of observations made in August, 1891, on the 
Holy Island sands. He counted the castings in nineteen 
measured areas, and found that the smallest number in 
any one of these areas was 8°2 per square yard, while the 
largest number was 42 per square yard. In both cases the 
castings were fairly large. In other two of these nineteen 
areas, Where the castings were very large (their average 
weight, when dried, being three ounces and two and a 
quarter ounces respectively), their numbers were 11 and 
14-5 per square yards respectively. 
At Musselburgh, on the Firth of Forth, there are 
extensive sands laid bare at low tide in which the sub- 
jacent layer contains a moderate amount of organic 
matter. Here worms and castings of large size are 
abundant near and for some distance above low-water 
mark. There are (January, 1904) about twelve to fifteen 
arge castings per square yard, the average weight of 
(eight of) which when dried is three ounces. In the 
course of a few minutes seven fine worms, the mean length 
of which was thirteen inches, in addition to other smaller 
ones, were obtained here. Although these sands have been 
visited almost daily for a long period of years by fishermen 
in search of bait, there seems to be no scarcity of worms, 
although probably over a thousand per day are, on an 
average, obtained. 
Near Portobello the beach near low water is gravelly 
in parts, and castings are scarce, but higher up the beach, 
‘ Geological Magazine, Vol. VIIT., 1891, p. 489. 
