50 



IOWA STUDIES IN NATURAL HISTORY 



TABLE 24 — The dry weight, organic matter, and ash of the worms 

 and various Crustacea are shown in this table. 



THE NANNOPLANKTON 



A relatively small number of forms was present in the 

 nannoplankton material, but two were found in consider- 

 able numbers. (See Table 25) . The ciliated Protozoa were 

 represented by Halteria and Vorticella; a comparatively 

 small number of each was found in the epilimnion while 

 the former was also found in the material from a depth of 

 83 m. Some specimens of Cryptomonas were noted in the 

 samples from 10 m. and 30 m. as well as Pandorina at 10 m. 

 Minute flagellated monads were distributed throughout the 

 depth of the lake, but they were much more abundant in 

 the epilimnion than in the other strata. 



Only two forms of algae were noted, namely, Aphano- 

 capsa and Oocystis. A small number of the latter was 

 found in the surface sample. The Aphanocapsa consisted 

 of small colonies of minute cells, 25 to 100 in number, em- 

 bedded in a gelatinous matrix. It seems to have a wide dis- 

 tribution since it appears in the nannoplankton of all of the 

 lakes of this country on which observations have been made. 

 It was found at all depths, but was most abundant in the 



