Trans. Wis. Acad., Vol. XL Plate XXXII. 



0- 3 m Mch. Apr. May. June. July. Aug. Sept. Oct. Nov. Dec. 



200 

 100 





























- V 



^*^s 































■ 



6- 9 m 



9-12 m 



12-15 m 



15-18 m 



Fig. 22.— Population of the 3 m. levels, 1895. Scale, 1 space = 100,000 Crusta- 

 cea. The 25.000 and 50,000 divisions are indicated. See page 387. 



