428 Si»io}i Henry Gage 



of June, that is, in the height of the running season. Some 

 males exhibited a ridge, but many none, so that it was not 

 possil:)le to distinguish the sexes with certainty by the external 

 appearance. 



In 1893 it was found that a fully mature lake lamprey ob- 

 tained April 10, that is about fifty days before the time for 

 spawning, showed none of the seasonal characters, and hence 

 it seemed likely as the spawning grounds of the true marine 

 lampreys were so far from the ocean, that some might set out 

 on their journe)' to them before any special, external sexual 

 characters appeared. To determine this, Mr. Holmes was 

 asked to secure the first lampreys that should be found run- 

 ring up the Merrimac, and also some at the very clo.se of the 

 sea.son. This was done during the present year (1893). 

 Tho.se caught about May 20, were found without either ridge 

 or anal fin, and the sexes could not be distinguished by any 

 external feature. On dissection, the sexual products were 

 found to be still firmly imbedded in the ovary and testis, or 

 spermary, and in many of them the alimentary canal was 

 large, .showing little or no signs of atrophy, except at the ter- 

 minal part. On July 8, there were received four specimens. 

 Only two were seen by Mr. Holmes after these were caught 

 so that those sent were among the last to ascend the stream. 

 These showed in an unmistakable manner the external char- 

 acters so striking in the two sexes of the spawning lake 

 lamprey, viz., a ridge extending from the gills to the dor- 

 .sal fin in the male and an anal fin-like crest in the female. 

 In both sexes the sexual products were partly shed into the 

 abdominal cavity. 



Information from the spawning grounds at the head waters 

 the Merrimac River in New Hampshire, shows that the dorsal 

 ridge has been noticed by those familiar with the lampreys in 

 that region. 



The dorsal fins in the male .especially, are in some cases 

 considerably approximated, but in only a few cases have the 

 marine lampreys .shown an appearance of continuity of the 

 two dorsals. 



It thus appears that the peculiarities so striking in the first 



