THE FISHES, MOLLUSC A, AND OTHER OBJECTS. 49 



apparatus. "Where there is duck-weed growing on 

 the surface of the water, there you may expect 

 to find this species in particular, in the greatest 

 abundance. The females are much commoner than 

 the males, and may be found throughout the year j 



Fig. 43. 



Daphnia schafferi (female). 



whilst the males are generally only to be obtained 

 in the autumn mouths. Dr. Baird enumerates 

 aeven British species of water-fleas, of which D. 

 9chce/eri is perhaps most common, next to D. pulex. 

 It may be readily known from the latter by its 



