BRITISH FRESH-WATER FISHES 



silvery-white in colour, with bluish or greenish on the 



back. It attains a maximum length of about i6 inches, 



and is a common inhabitant of many of our larger rivers, 



especially the Severn. It has only one nasal opening, 



but makes up for this by having seven small gill-slits 



on either side of the body at the back of the eye. There 



are no fins along the front two- thirds of the body-length, 



and even then only a small, succeeded by a larger one, 



is present on the back, and the pointed tail is more or less 



finned above and below. Lampreys possess a sucking 



disc, and with this they attach themselves to their prey. 



It seems agreed that they belong to a very low type of 



animal life, but in spite of this their metamorphosis is 



most interesting, and we have a good deal to learn 



respecting them. Some individuals appear to spend 



their whole time in fresh water, others proceed to the sea, 



ascending rivers, like the Salmon, for spawning. This 



latter event happens in Autumn or Winter, and the 



Lamperns, as they are also called, gradually make their 



way nearer the source of rivers until they have travelled 



so far that only small tributaries of the main artery 



are occupied. They delight in a gravelly bed, and 



are of social habits, for little companies of thirty or 



forty assemble together in Spring and early Summer. 



Although so low in the scale of life. Lampreys construct a 



" nest," and it is interesting to note that several pairs 



will share the one abode. Their ideas on co-operation are, 



to say the least, put to a very practical test. A word 



should be written as to the " nest " as it merely consists 

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