CHANGKS IN ENVIRONMENT 0¥ DAPHNIA MAGNA. 



213 



tively small volumes of water with no circulation, the spine 

 appeared to gradually diminish in length. Continued obser- 

 vation then proved that at the end of six months or so a 



i'lG. 



A. A Daplinia with a fairly lonj^ spine. 



B. Au individual in wbicli the spine is absent. 



colony of Daphuia in a large bell glass would possess exceed- 

 ingly small or no spines. 



Some experiments were now undertaken to determine 

 the rate at which the spine diminishes, and the volume of 

 water which produces this reaction. Daplinia were placed in 

 a known volume of water, and the length of the spine in 

 successive generations was measured. 



