PKOCEEDINGS: BIOLOGICAL SOCIETY 79 



larvae are parasitic in earthworms in France. Dr. Howard is having 

 large numbers of earthworms examined for such larvae, but so far 

 without success. He hoped that anyone finding any grubs parasitic 

 in earthworms would communicate with him. 



The first paper of the regular program was by Dr. Charles H. T. 

 Townsend, "Identification of the stages in the asexual cycle of Bartonella 

 bacilliformis, the pathogenic organism of verruga, and their bearing on 

 the etiology and unity of the disease." (Published in full in this Journal, 

 5: 662-667, December 19, 1915.) 



The second and last paper of the program was by A. A. Doolittle, 

 "The Mississippi River dam at Keokuk, Iowa: Its effect upon biological 

 conditions, especially those of the plankton. The speaker stated that the 

 Bureau of Fisheries has been examining the new conditions caused by 

 the damming of the Mississippi River at Keokuk, Iowa, to develop 

 electric power. The water is raised to 40 feet above of the river 

 gauge at Keokuk, that is, to the 525-foot level above sea. The water 

 power company must maintain the lake between the 519 and 525-foot 

 levels. The effect of the dam runs out at Oquawka, 111., 54 miles from 

 Keokuk. In the lower third of its course Lake Cooper, as the im- 

 pounded waters are called, fills the gorge of old Des Moines Rapids. 

 In the middle third of its course is the greatest lateral expanse, 4 miles 

 or more, covering much island and farm lands. Forests are removed 

 from only a little of the submerged area. Water persicaria seems to 

 be the only water weed establishing itself in great quantity. In the 

 upper third the threatened banks are being enclosed by levees and will 

 be drained by pumping stations. Tributaries are filled for some dis- 

 tance from the river-lake, the larger ones being navigable for upwards 

 of 3 miles in small launches. 



There are present the usual characteristics of a river lake : increased 

 regularity of water stages; decreased current; decreased turbidity; 

 establishment of rooted aquatic plants. The most immediate effects 

 of economic importance, biologically, are the destruction of the famous 

 mussels of the rapids, and the interference with the usual passage of 

 fish up and down the river, especially the periodic migrations. 



The dominant zooplankton were several species of Entomostraca 

 (Moina, Diaphanosoma, and Cyclops viridis); the phytoplankton in- 

 cluded Conferva spp., Anabaena spp., and Clathrocyctis. Estimates 

 of the abundance of plankton were based upon the cubic yard. Above 

 the influence of the dam about 50 entomostracan individuals con- 

 stituted the plankton, with traces of algae. At Keokuk this was in- 

 creased in July to 1500 individuals, in August to 270,000 (volume 

 estimated at 26 cc), and in September to 1500. Green algae measured 

 0.14 cc. in July, 29 cc. in August, and 5 cc. in September. Blue-green 

 algae measured traces in July, 2.6 cc. in August, and the same in early 

 September. Below the dam at the maximum for the season the run- 

 off contained 3,000 Entomostraca per cu. yd., 1.17 cc. green algae, 

 and traces of blue-greens, a marked enrichment over that of normal 

 river conditions. In weedy waters, additional heavy-bodied Euto- 



