14 Trans. Acad, Sci. of St. Louis 



these minute crustaceans it must have been highly 

 charged with the products of organic decay but this 

 water did not have a disagreeable odor and this creature 

 has been found flourishing in fetid water. Has not the 

 marvelous prolificacy of this species, co-operating with 

 the rapid evaporation of the water, caused the popula- 

 tion to outgrow its food supply and thus to induce a 

 famine which caused universal sexual impotency fol- 

 lowed by death? The few individuals of Cyclops ser- 

 rulatus Fischer which were found in the pond soon after 

 the catastrophe were dwarfs of their kind. This is in 

 harmony with the above conclusion, for excessive reduc- 

 tion of the food supply means underfed naupli, and 

 underfed naupli develop into undersize adults. 



As stated above, these seasonal life histories are re- 

 corded for the purpose of showing that a study of the 

 succession of life in ponds and marshes, for only one or 

 two seasons, does not furnish sufficient data to warrant 

 the formation of scientific conclusions concerning the 

 succession of life in inland waters. These two records 

 have certain things in common. When winter gives place 

 to spring there is very little life in the pond. Species 

 after species appears, each to remain for a longer or 

 shorter period of time. Some cladoceran or copepod 

 becomes the dominant form. The living individuals con- 

 tiuously become more and more numerous until the his- 

 tory culminates in a catastrophic elimination of almost 

 the entire population. This is about all the two years 

 have in common. In April, 1920, the first forms to be- 

 come conspicuous are Simocephalus serrulatus (Koch) 

 and Cyclops viridis (Jurine), neither of which is domi- 

 nant; in April, 1921, the first to appear are Cyclops al- 

 bidiis (Jurine) and Cyclops viridis (Jurine), the former 

 of which is dominant. In 1920 Simocephalus serrulatus 

 (Koch) becomes dominant in the early part of May and 

 retains the dominancy until the latter part of June, when 



