142 C. ISHIKAWA. 



The earlier forms in spiing are, as usual, all partheiiogeiietic females, 

 but in course of summar months the males and the gamogenetic females 

 are very often to be met with. The exact numbers of the different 

 generations are, however, not as yet clearly made out. 



In the same ponds are also very abundantly found two species of 

 Moina, but they always keep their colonies quite separate from that of 

 Daphnia as from each other, and each seems to thrive very vigorously. 

 The co-existence of Moina and Daphnia in small places, seems, however, 

 to be disastrous to the latter animal, as was shown in my aquariums 

 where Daphnia always disappear at the presence of Moina. The same 

 fact was also observed previously by G. O. Sars* with his Australian 

 Daphnia Lumholtzii and Moina propinqua. 



Explanation of the Plate. 



Daphnia Morsei, n. sp. 



Fig. 1. Parthenogenetic female. Seibert's objective I, eye-piece 1. 



Fig. 2. Another parthenogenetic female, viewed from the dorsal side. Zeiss' ob- 

 jective A, eye-piece 2. 



Fig. 3. Gamogenetic female. Seibert's objective I, eye-piece 1. 



Fig. 4 Male. Seibert's objective f, eye-piece 1. 



Fig. 5. Left shell-gland of a parthenogenetic female. Zeiss' objective B, eye- 

 piece 2. 



Fig. 6. Post-abdomen of a parthenogenetic female. Zeiss' objective B, eye-piece 1. 



Fig. 7. Caudal spine of the same. Zeiss' objective D, eye-piece 2. 



Fig. 8. Posterior end of the left c irapace of a parthenogenetic female. Zeiss' ob- 

 jective D, eye-piece 1. 



Fig. 9. Optical section of a piece of the carapace. Zeiss' objective D, eye-piece 4. 



• On some Australian Cladocerii, raised from Dried Mud. Christiania Videnskabs- 

 Selskabs Forhandlinger 1885, Xo. 8 



