SEA-FISHERIES LABORATORY. 391 
is better, however, to term it simply “ digestive gland,” 
for it is evident from experiments that it secretes ferments 
which perform functions that are specialised in separate 
organs in higher animals. It is conspicuous both from 
its size and its very dark colour, due to the contained 
pigment. The gland itself is of a more solid consistency 
than is usually the case in Molluscs.’ It lies dorsally to 
the adductor muscle, against the hgament, which causes 
a depression on its surface. 
The gland completely wraps round the large 
stomach, and there is no sign of a division into two lobes 
in its compact mass except that the ducts open in two 
series laterally into the stomach, as has already been 
pointed out. 
The gland may be fixed for sectioning in Flemming, 
Mann’s Fluid or by McMunn’s method, that is by placing 
pieces of fresh gland in 20-30 per cent. formol for 12-14 
hours, and then in 95 per cent. alcohol. 
The green pigment can be seen am setw whether fixed 
in formol or by Mann's Fluid, though it is dissolved out 
readily by spirit, if placed directly into it. 
It (fig. 50) is a tubular gland formed by the ducts 
dividing up into numerous branches, which, ramifying 
on their way, divide still further to form caeca. 
In Pecten this makes up practically the whole of the 
gland, for there is no great development of vesicular 
connective tissue as seen in the oyster. Moreover, in the 
latter the secreting alveoli are to be seen in sections as 
tubes with a considerable cavity. In Pecten they are 
very short, and soon become wholly solid in character, so 
that the first difference which one notes on comparing 
sections of the two glands is the solidity of the one and 
the tube-like alveoli of the other. It is difficult to divide 
the cells lining the ducts into different categories, for one 
