12 Trans. Acad. Sci. of St. Louis 



ant, Simocephalus serrulatus Koch and Oxyurella tenuicaudis (Sars) 

 present in small numbers. 



July 20. Pond drying up rapidly; no vegetation in the water; 

 temperature 35 °C.; animal life very scare, a few specimens of Cy- 

 clops viridis (Jurine) var, insectiis Forbes and of Diaphanosoma 

 brachyurum (Lievin) found. 



August 17. Pond nearly dry and entomostracan life has almost 

 disappeared, a few specimens of Cyclops serrulatus Fischer found. 



Spring and summer 1921. — April 2. Pond moderately high; no 

 vegetation in water; temperature 19 °C.; hydrogen ion content PH 

 7.9; Cyclops albidtis Jurine the dominant form; Cyclops viridis 

 Jurine var. insectus Forbes abundant. 



April 16. Pond moderately high; temperature 19°C.; hydrogen ion 

 content PH 7.0 (a heavy rain having fallen the previous night) ; Cy- 

 clops viridis (Jurine) var. insectus Forbes and Cyclops serrulatus 

 Fischer abundant, neither dominant, Cyclops albidus Jurine has al- 

 most entirely disappeared, 



April 23. Water high owing to heavy rains; temperature 17 °C.; 

 hydorgen ion content Ph 7.4; Cyclops viridis (Jurine) var. insectiis 

 Forbes dominant, Cyclops serrulatus Fischer abundant. 



April 30. Conditions about the same as on April 23; Cyclops 

 viridis (Jurine) var. insectus Forbes the dominant form, Cyclops ser- 

 rulatus Fischer abundant, Bosmina longirostris (O. F. Mueller) pres- 

 ent in small numbers. 



May 11. Water at greatest height; grass growing in water; tem- 

 perature 22°C.; hydrogen ion content PH 7.4; distribution of life 

 about the same as on April 30, although BosmAna longirostris (O. F. 

 Mueller) Sars may be more abundant. 



May 20. Physical features about as on May 11; Cyclops viridis 

 (Jurine) var. insectus Forbes dominant, Bosmina longirostris (O. F. 

 Mueller) abundant, Cyclops serrulatus Fischer has disappeared. 



June 1. Water falling; hydrogen ion content PH 8.2; Cyclops 

 viridis (Jurine) var. insectrus Forbes dominant, Bosmina longirostris 

 (O. F. Mueller abundant, Cyclops fimbriatus Fischer, Macrothrix lati- 

 comis (Jurine) and Scapholeberis mucronata O. F. Mueller present 

 in small numbers. 



July 5. Water lower, otherwise physical conditions same as on 

 June 1; Cyclops viridis (Jurine) var. insectus Forbes dominant and 

 present in enormous numbers, Moina brachiata (Jurine) abundant; no 

 Other cladocerans nor copepodans. 



July 19. Water quite low, otherwise physical conditions same as 

 on July 5; no perceptable change in life conditions. 



July 27. Pond quite shallow; hydrogen Ion content PH 7.2; 

 literally thick with entomostracan life confined to the two species 

 Cyclops viridis (Jurine) var. insectus Forbes and Moina brachiata 

 (Jurine), the former dominant, all other cladocerans and copepodans 

 absent or so scarce as to escape detection among the myriads of the 

 two species mentioned; the Molnas bearing summer eggs but the 



