FISHERIES, GAME AND FORESTS. 201 



same sand-bar and showing no evidence of grouping in sizes according to age. It 

 would appear that their growth depends upon their food supply, and the largest of 

 last year may be as large as the smallest of the preceding year. The duration of the 

 larval period is not known, but we believe that it is three or four years. The current 

 frequently shifts the sand of their bed and washes them down and into the sediment 

 along the shore. The best place to find larval lampreys is some distance below the 

 spawning beds, in the deposit of light silt and organic material near the shore, where 

 the stream is filling up in the concave side of a curve in its channel (see illustrations 

 Nos. 1 1 and 12). We have often found them abundant and of various sizes in such a 

 place, fully a mile down stream below the lowest favorable place for a spawning bed. 

 Such is the location of the place here shown, where we have found scores of immature 

 lampreys. 



The mouth of the young is covered with fimbriae or lamellae, which are so 

 close together as to act as a sieve and prevent the passage of grains of sand. This 

 makes it possible for the young lamprey to eat only the most minute organisms, and 

 the latter must be taken while the larva is blindly making or following its sinuous 

 path through the sand, or they are taken in with water. 



The larvae of the two species found here are so nearly alike that constant charac- 

 teristic differences have not yet been pointed out. It is known, however, that at the 

 time of metamorphosis the larvae of the Brook Lamprey are much smaller than those 

 of the Lake Lamprey. 



The Transformation. The transformation is remarkable and interesting, and finds 

 its parallel only in the wonderful changes that ensue in the metamorphosis of a tadpole 

 to an adult frog or toad. 



The larval lamprey is entirely blind, toothless, externally segmented, and lives 

 altogether beneath the surface of the sand, feeding only upon microscopical organisms, 

 through a mouth that is covered and sieve-like. Of course, as their food is such 

 minute material and is captured in such small quantities, the amount of their 

 nourishment is limited and their growth is necessarily slow. It is not known just how 

 long thev remain in the larval stage, but it must surely be three years at least, and 

 possibly four. This should be determined. If we had a State Biological Station, 

 such questions that are of real economic value could be readily determined. The 

 necessity of such knowledge is apparent when we realize that any experiments toward 

 exterminating these pests must be continued through as many years as there are in 

 the life history of the lamprey, from the egg to the spawning adult. If this is five 

 years, and we believe it is, it means that there are five generations in existence 

 at any one time, overlapping one another, and each differing from the other by at least 

 one year's growth. 



