CHANGES I\ ENVIRONMENT OF DAPHNIA MAGNA. 



201 



On April 17tli the individuals of second series under the 

 ground glass had attained a size of 2'94 mm. and o*14 mm. 

 and had produced forty-seven offspring. Those under green 

 light were 2'6b, 2* 11, 2'43 mm., and there were five young. 

 Under blue light 2*48, 2'43 mm., and six young. In the dark 

 2"36, 2'45 mm., and there were two young. 



The individuals which had been living in green and blue 

 light and in the dark succumbed much quicker to "5 per cent. 

 NaCl than those which had been living in red light or under 

 ground glass. I hope, however, to deal with the subject at 

 greater length on a future occasion. 



Daphnia have a very low power of becoming acclimatised 

 to salt. 



Daphnia living in a small confined volume of water are 

 shown to gradually lose their spines (see fig. 3). The experi- 

 ments described prove that if an animal be allowed to grow 

 up in 40 c.c. of freshly drawn water, its spine would on the 

 average be shorter by several hundredths of its body length 

 than if it had lived in an unlimited bulk. 



The sudden transference from water containing more 

 mineral constituents to water containing less, and vice 

 versa, is apparently not without effect. 



Living in a small confined volume of water is shown to 

 have a great influence on the rate of growth and reproduc- 



