2l8 REPORT OF THE COMMISSIONERS OF 



or diagnostic attribute of sex, season, or condition. All that can definitely be said is 

 that representatives of either sex may or may not be thus highly colored, and after 

 having carefully watched them for some consecutive years, we are prepared to say 

 that a greater number of males than females regularly possess this coloration, and in 

 the early part of the season there is a much larger percentage that is highly colored 

 than later. Nearly all that run early are well colored, while the percentage of those 

 of somber or dark appearance gradually increases until the end of the season. This 

 may be due to the fact that the coloration is most marked in the largest and most 

 vigorous specimens of each sex — although there may be seen many very large 

 individuals of either sex that are not highly colored — and the individuals with 

 greatest vitality are those that first mature and run up to spawn. This is but an 

 example of a law of all organisms. The most perfect blossoms expand first and 

 exhibit the brightest colors ; the finest fruits ripen earlier than those that are less 

 perfect, even on the same tree, and have the brightest colors and best flavors; the most 

 vigorous animals of any kind are the first to arrive at complete maturity, and they are 

 the individuals that present the best colors and finest appearance. 



We know of no kind of animal of which the individual representatives exhibit such 

 widely differing coloration when at the same stage of reproductive maturity as do 

 those of the Lake Lamprey. It is so marked, with such absence of intergrading forms, 

 that it almost amounts to a dichroism, such as is seen in the screech owl. In the same 

 nest there may be found mating lampreys, either sex of which may present the high 

 coloration while the other may not ; or they may both be rufous or both very dark or 

 quite somber. The larger individuals are very likely to be colored, while the smaller 

 ones are very rarely so. Toward the end of the spawning season the color gradually 

 fades out. It has not been found to especially predominate in either sex, and during 

 the past four years it certainly has not shown any tendency to alternate in accordance 

 with the sex of the lamprey. 



What ends of the creature can be served by this rufous coloration ? This has been 

 asked, but not answered. We believe it to be protective coloration, especially when 

 lampreys swim over the bottom that is covered with brown algse and iron rust, as is 

 most of the bed of the stream. Their color is such that as they lie upon the kind of 

 a bottom mentioned it is almost impossible for even a careful observer to discover 

 them, and a glint of sunshine, broken by the rippling waters, renders them especially 

 inconspicuous. While the darker or more somber-hued individuals do not thus blend 

 with the color of the undisturbed bottom, they in turn are less conspicuous while in 

 the nests, which are darker than the undisturbed stones. We have observed highly 

 colored individuals, when pursued, leaving their nests, and later returning and clinging 

 to the reddish brown stones in the bed of the channel near them. 



