The Lake a?id Brook Lampreys of Neiu York 439 



appears like a thread. As no food is taken during the spawn- 

 ing season there is no necessity for digestion, and in the fe- 

 male there is no room for the intestine when the ova are com- 

 pletely matured. This is not the cause of the atrophy, how- 

 ever, for in the male the increase in size of the spermary is 

 less marked than of the ovary in the female, leaving plenty 

 of room for the intestine, still it in many cases is as markedly 

 atrophied as in the other sex. 



While the atrophy of the alimentary canal is going on there 

 are certain hypertrophies taking place, differing somewhat in 

 the two sexes, and in the two species. In the male of the 

 lake lamprey there occurs a great increase of the connective 

 tissue along the dorsimeson. This begins about opposite the 

 middle branchiopore and extends to the dorsal fins. This 

 hypertrophy gives rise to a rounded ridge along the back, 

 thus adding a very striking feature to the spawning male (PL 

 III, fig. 5, PI. VII, fig. 31). As an extension of this hyper- 

 trophy, the two dorsal fins are approximated to complete 

 fusion in most cases, but apparently no new fin rays are de- 

 veloped. The increa.se in the connective tissue along the dor- 

 simeson in the female is not marked, except that perhaps the 

 two dorsals appear somewhat approximated. "With the female 

 there is a marked hypertrophy in the tissue around the vent 

 thus giving rise to a kind of notch, there is also developed a 

 fin-like fold between the vent and the caudal fin making the 

 caudal fin appear to extend to the vent as in the larvae of 15 

 to 20 millimeters in length. In both sexes the urogenital pa- 

 pilla is always present, but in the breeding season it is ex- 

 tended in the male so as to project beyond the level of the 

 body (PI. Ill, fig. 6-8). 



The abdomen of the female increases markedly in diameter to 

 accommodate the maturing ova ; also as shown by the preced- 

 ing tables, there seems to be an actual increase in the length of 

 the abdomen, thus shortening the tail. With the male, on 

 the other hand, the abdomen appears to become relatively 

 shorter and the tail longer. 



The coloration of the lamprey is very modest out of the 

 breeding season, but in the breeding sea.son there is a great 



