132 
red. Older specimens, especially if taken from sand in 
which the amount of organic matter is considerable, are 
nearly black in colour and their gills, which are also 
pigmented, are better developed than in young specimens. 
The second variety of A. marina is found in the upper 
part of the Laminarian zone, and can only be readily 
obtained at very low tides. It breeds in the spring, from 
the beginning of March onwards.t = When fully grown 
it is one of the largest Polychets of our shores, measuring 
as much as 400 mm. (16 inches) in length and nearly three 
inches in girth at its widest point. It is dark brown or 
almost black in colour. Its burrow, in which the worm 
is found head downwards, appears to be simply vertical 
and not U-shaped. The most distinctive character of this 
variety is, however, the gill, which is a highly developed 
pinnate structure (fig. 19) consisting of about twelve stems 
united by a connecting membrane at their bases and 
bearing ten or more branches on each side of the axis. 
The Laminarian differs from the littoral form also in the 
sub-division of the interval between the second and third 
chetigerous annuli; in the former this region is divided 
into two rings and in the latter into three (see figs. 1 and 
2) 
~/. 
There do not appear to be any other structural points 
of difference. The Laminarian variety is abundant on 
certain parts of the Lancashire coast, ¢.g., near Blackpool, 
where specimens are obtainable at low tides on digging to 
a depth of about three feet in the sand near extreme low- 
water mark. I have recently found four specimens* of 
this variety in a collection of Arenzcola from the sand 
between Portobello and Musselburgh on the Firth of 
Forth. The Laminarian variety has also been found in 
+ See footnote (+) on p. 131. 
* The gills of two of these were not as obviously pinnate as those 
of the Laminarian forms of the Lancashire coast, 
