The Lake and Brook Lampreys of New York 429 



lake lamprey obtained, are present in the males only, and are 

 seasonal and very temporary. Furthermore, in addition to 

 the characters mentioned above as common to the sea and the 

 lake lamprey, the determination that in the true marine 1am- 

 prej's similar sexual peculiarities occur at the breeding season, 

 removes the last element of doubt as to the very close relation- 

 ship of the lacustrine and marine forms. 



With reference to the specific identity of the lake and the 

 marine lamprey, it seems impossible to doubt that they were 

 originally identical, and that the lake lamprey in its somewhat 

 isolated, inland home has become considerably modified. The 

 most salient and important modifications relate almost wholly 

 to the adult form so far as is known ; for the larvae of the sea 

 lamprey from the Susquehanna River agree so closely with 

 those of the lake that if several living or similarly preserved 

 specimens of about the same size from each locality were 

 mingled, it would be difficult or quite impossible to again 

 separate them. This argument may not be of great import- 

 ance, however, for as it will be shown later, no definite dis- 

 tinctions between the larvae of the lake and of the brook lam- 

 prey have yet been discovered. The modifications in the 

 adult form are : (a), A very much smaller size for the lake 

 lamprey ; the average length in the breeding season being fre- 

 quently less than half that of the sea lamprey. The dorsal 

 ridge is relatively much more prominent in the male lake 

 lamprey in the breeding season than is that of the sea lamprey, 

 and the two dorsal fins are more nearly fused ; likewise the 

 urogenital papilla of the male, the notched appearance at the 

 vent and the anal, fin-like fold in the female are relatively 

 greater in the lake than in the sea lamprey. There is more 

 frequently a larger number (8 to 9,) cusps or teeth to the infra- 

 oral lamina, or the mandibular tooth-plate, in the lake lamprey 

 than in the sea lamprey ; and finally there is a greater devel- 

 opment of cutaneous pigment and it is more diffusely arranged 

 so that the general coloration of the lake lamprey seems more 

 uniform, and on the whole somewhat darker than with the sea 

 lamprey. Indeed, the marine lamprey is designated by the 

 fishermen as the large spotted lamprey. 



