Since there is no evident repair or replacement of the lost 

 layers, the scarring effects of all abrading agents are cumala- 

 tive. Some dying individuals were almost coropletely denuded 

 of the outer layer of skin. These conditions rendered the sea 

 lampreys very vulnerable to fungus infections., -which many dis- 

 played. 



(3) Degeneration of the digestive tract and change s 



in the color of the liver 



TvTo changing phenomena are readily apparent in the dissec- 

 tion of sea lampreys collected during the entire season of mi- 

 gration and spaivning. One is a series of changes -yrhich occurs 

 in the color of the liver; the other is a striking reduction in 

 the size of the digestive tract. 



The liver of sexually immature and actively feeding adults 

 is normally a pale reddish-orange » Among male sea lampreys the 

 livers of the earliest migrants still retain this color. Hotr- 

 ever^ as the migratory season progresses and the run is composed 

 of individuals in more advanced stages of sexual maturity, a 

 series of color changes of this organ appears. Successively, 

 the color of the liver becomes orange-yellow, sometimes mottled, 

 sometimes of a uniform intermediate shade j yellow| yellow-green, 

 either mottled or of a uniform intermediate shades and finally, 

 a bright, li^t green. The livers of virtually all male migrants 

 examined during and after the peak of the spa"wning run were in 

 advanced stages of changei the colors occurring were yellow, 

 yellow-green, or light green. The color cf the liver of all 

 spawning and spent males examined was light green. 



The liver color of the earliest migrant females likewise 

 is the reddish-orange characteristic of the organ in sexually 

 immature adults, although it is of a somewhat darker shade. 

 Changes in the color of the liver mth increasing sexual matur- 

 ity differ from those cf the males arid are less elaborate. The 

 liver in migrant females on successive dates becomes: reddish- 

 brovm, brownish-green, either mottled or cf an intermediate 

 shade; and finally, dark green. In the latter half of the run, 

 all females fell in the last two color categories. The livers 

 of all spawning and spent females are dark green in color. 



These color changes of the liver are very pronounced in 

 character and differ so distinctly between the two sexes that 

 accurate sex determinations can be made upon sexually maturing 

 or mature adults solely upon an examination of the color of this 

 organ. 



When the above observations were made, records were obtsi:ied 

 of the stage of sexual maturity, color of the liver, and in- 

 testinal and rectal diameters of 1|78 male and female sea lampreys 



- 120 - 



