The Lake ajid Brook Lampreys of New York 453 



^th the length and probably not one y^th bulk of the spawn- 

 ing ones. The gonads are small and the ovary and ova are 

 minute but perfectly recognizable on transforming. The com- 

 parative size is given on plate vii. The gonad of the male is 

 very small indeed, and the sperm mother-cells not far ad- 

 vanced. To attain the size and maturity of the spawning 

 ones it is believed that two or three years are required. This 

 conclusion is reached by the size and development of indi- 

 viduals caught in various months of the year. For example, 

 while the lake lamprey is spawning, specimens have been 

 taken from the lake with the intestine large and full of blood 

 and with ova of about half or one-third the size of the mature 

 ones. In others of about 200 or 225 millimeters length the 

 ova are still smaller. The smallest ones are supposed to have 

 transformed six to eight months previously and those next in 

 size a year and a half earlier. The absolute bulk of fishes de- 

 pends so largely upon the food supply that size of body alone 

 is not a good test of maturity. The size and stage of develop- 

 ment of the sexual organs is a safer guide. Following this 

 guide it seems very probable that it requires either one year 

 and a half, two years and a half, or three years and a half for 

 the small, just transformed larva of 150 millimeters to attain a 

 length of 450 millimeters, or rather that ova of the size shown 

 in plate vii, figure 34 A, require that time to reach the size and 

 maturity of the egg shown in 32 A. This question like those 

 previously mentioned can be definitely settled only by rather 

 expensive experimentation. That it has an important scien- 

 tific interest all biologists will agree ; that it also has a very 

 important economic bearing may be seen also when one reflects 

 how many food fishes are either destroyed or greatly weak- 

 ened bj' the parasitic adult lampreys. 



The transformation of the larva into the adult is usually 

 described as taking place in a few days. In three or four (en 

 trois ou quatre jours) according to Bujor ('91), for the Euro- 

 pean brook lamprey (P. planeri, or P. branchialis). The time 

 given by Miiller is longer, 10 to 26 daj'S. My own observa- 

 tions accord more with those of Miiller. The first external 

 signs of transformation is the appearance of the eyes upon the 



