456 Simon Henry Gage 



larval organs like the velum atrophy. So far as the liver and 

 its duct are concerned it is almost universally stated that in 

 the Kuropean brook lamprey the bile duct loses its connection 

 with the intestine upon transformation. This is not the con- 

 dition in the lake lamprey and in many examples, at least of 

 the sea lamprey. It is only upon the atrophy of the intestine 

 at the breeding season that the bile duct is occluded. Then 

 the liver assumes an emerald green color as stated above (p. 

 438). From the numerous observations made by the writer 

 on transforming lake lampreys and sea lampreys from the 

 Susquehanna River, there is not a period of quiescence com- 

 parable to the pupa stage of insects ; such a period would be 

 expected with so great a histolysis and subsequent histo- 

 genesis as described by Bujor ('91) for the European form of 

 the brook lamprey. 



In collecting the transforming lampreys the same method is 

 employed as described above for the untransforming larvae. 

 It is well, however, to have a dip net with a long handle, for 

 the transforming ones more readily leave the sand when it is 

 disturbed by the shovel, and attempt to swim awa^- in the 

 stream. With the dip net these may frequently be caught. 



Up to the present time there has been no waj^ discovered of 

 distinguishing the larvae of the lake and of the brook lamprej'. 

 As the two species occupy the same spawning ground and 

 sometimes spawn in the same nest great care is necessarj' in 

 order not to confuse the two. After the larvae leave the nest 

 they apparently go to the same sand bed. There are certain 

 peculiarities about the one figured in plate iv that might lead 

 one to diagnose it as the larva of a brook lampre\-. Here 

 again, only a carefully conducted experiment would give 

 definite and reliable information. 



If one can keep the transforming ones alive until the dental 

 papillae appear on the oral disc the distinction is as clearly 

 marked in the two species as in the adult, for there is the 

 same definiteness of arrangement, and the same arrangement 

 of dental papillae in the young as in the horny teeth of the 

 adult. The general appearance of the brook and the lake 

 lamprey is also as strikingly unlike at this stage as in any sub- 

 sequent one. 



