2 University of Michigan 



but it is also likely that different species vary with respect to 

 the length of the life cycle and that the same species may vary 

 in different localities. 



Miiller (1856), who is usually credited with the discovery 

 that the ammocoetes are the larval forms of the lampreys, 

 measured six larvae of the European brook lamprey, pre- 

 sumably Lauipctra planeri, and found their lengths to be 5.8, 

 6.3, 6, 15.3, 15.4, and 14 centimeters, respectively. The firsi 

 three he judged to be a little over a year old and the last three 

 about two years. Two metamorphosed individuals measured 

 16.2 and 19.3 centimeters each, and he concluded that these 

 must be at least over two years old and would be three years 

 at the time of spawning. 



In the same species, Lubosch (1903) found larvae of three 

 different sizes. Those of the first few months measured from 

 one to two centimeters in length. The average size of larvae 

 of the first year was five centimeters, that of the second year 

 larvae ten centimeters, and that of the third year larvae, or 

 just before metamorphosis, fifteen to eighteen centimeters. 

 He thus agrees with Miiller regarding the length of the life 

 cycle in this species. 



Loman (1912), on the other hand, found larvae of four 

 different sizes in single collections of this species, and he 

 believed that these represented four different generations. No 

 mention is made of the season when such collections were 

 made, so it is not possible to tell whether he meant to imply 

 that the life cycle is four or live years. 



Larvae of the American brook lamprey, Bntospheniis appen- 

 dix,- collected near Ann Arbor, Michigan, were found by 

 Schaffner (1902) to be of three different sizes just before the 



- The species commonly known as Lampetra or Entosphenns zvilderi. 

 See Creaser and Hubbs (1922). 



