51 



So far, however, we have not been able to obtain mature fish, or 

 to get any information as to the places of spawning, although 

 we have the abundant evidence of the table to show that spawning 

 takes place on a hirge scale at many places in the Tyne and its 

 tributaries. 



I am writing the above in the hope tliafc this note will draw 

 attention to the matter, and that soon the problem as to the adults 

 wU be solved. 



I add to this paper a diagram showing the results of the 

 measurements which have been made in length to various parts 

 of the bod}^ as indicated. It will be seen that there is much 

 variation, a great deal of which is no doubt actual, but some due 

 to the difficulty of measuring such small examples. The general 

 trend of the measurements is in all cases a straight line one, although 

 it is not so consistent as in the case of the measurements of larger 

 fish, long past the metamorphosis. In the table I express the 

 average measurements in terms of the tangents of the angles 

 represented by these lines. Mr. F. Arthur, Maldon, sent me a 

 consignment of fresh water lampreys, Lampefra fluviatilis, and 

 these were measured in the same manner, and when converted 

 in the same way into tangents they gave the numbers indicated: — 



TYXE LAMPREYS. 



It will be seen that so far as the posterior measurements of the 

 body are concerned there is a fair amount of agreement, but the 

 nose and the first gill are very difierent in position in the adult 

 as compared with the larva. This is probably due to the changes 

 which take place during metamorphosis, and at all events it would 

 not be safe to argue that they are due to the Tyne species being 

 Planer's lamprey. There can be little doubt from the reports 

 that have been made that it is the larger species v/hich frequents 

 the Tpie. 



