416 



Birge — The Crustacea of the Plankton. 



In 1897 similar observations were made by the aid of the 

 pump; 40 liters of water being ordinarily pumped from 

 each level. The results were substantially the same, al- 

 though the number of Crustacea found in and above the thermo- 

 cline was smaller, since the population of the lake was smaller 

 in 1897 than in the preceding year. The following table shows 

 the results of some of the observations. It will be noticed that 

 the abruptness with which the Crustacea stop is evidence that 

 the pump did not draw water from any considerable distance 

 from the mouth of the suction hose. 



Table XXXIX.— Typical catches from the thermocline stated in thousands per 



cubic meter. See also Table XXXVIII. 





w 

 u 



CD 

 43 

 CD 



a 



,4" 



ft 



CD 

 P 



9 

 10 

 11 

 12 

 13 



11 

 12 

 13 



11 



12 



12.5 



13 



14 



10 

 11 

 12 

 13 

 14 

 15 



CD 

 U 



43 

 «S 



u 



CD 

 ft 



a 



CD 



H 



03 







a 



o 



43 



ft 



«3 



P 



CO 

 ft 

 O 

 i— 1 



o 

 >> 



Q 



CG 



a 

 P 



eS 

 > 

 u 



O 



o 

 tn 



43 



CD 

 U 



P 



M 



.pH 



U 



a 

 a 



•iH 



i— 1 



ft 



p 



8.7 



a 



o 



CO 



O 



a 



el 



ft 



eS 

 P 



CO 





 r— 1 



'co 



be 

 u 



eS 

 u 

 O 



o 



43 



ft 



CD 

 r-3 



*p4 

 O 



ctt 



43 



CO 

 

 U 



o 



I— 1 



rt 



43 

 O 



'ft 



ctj 

 h 



43 

 CD 

 U 

 O 



o 



r 



A. 1 

 Aug. 17. Sur-J 

 face tempera- j 

 ture, 21.8°. 



21.6° 



21.5 



17.5 



15.9 



15.1 



20.6 

 19.0 

 15.0 



21.3 

 21.2 

 20.4 

 16.2 

 15.0 



20.5 

 20.4 

 17.6 

 15.6 

 15.0 

 13.0 



8.7 

 6.0 



7.6 



8.8 

 4.8 

 4.0 



6.8 

 8.7 

 1.8 



0.2 

 1.5 

 0.5 



4.8 

 5.3 

 0.3 



0.8 

 1.3 



0.05 

 0.05 

 0.02 



50.5 

 53.1 

 24.7 



28.6 



4.1 



3.2 



11.8 



5.8 



0.05 



0.1 

 15 



1 













2 



b. r 



1.0 

 1.0 



10.2 

 7.8 

 2.4 



0.05 



1.4 



2.5 



1.3 



0.05 



0.05 



5.0 

 5.0 

 1 



8.4 



13.8 



29.3 



0.1 



0.05 



7.8 

 9.2 

 13.2 

 0.1 

 0.1 



5.0 



2.8 







4.3 

 1.5 







15.3 

 12.1 



0.1 



24.6 



23.3 



34.5 



0.2 



0.15 



16.7 

 22.4 

 25.5 

 0.17 

 0.25 



9.2 

 10.0 



11.4 

 11.1 



16.5 



19.5 

 42.5 

 34.4 



0.2 





Aug. 25. Sur-J 

 face tempera- 1 

 ture, 22.7°. 







1.8 











0\08 



r 



3.0 

 7.2 

 1.6 

 0.1 

 0.05 



5.0 



8.2 



1.0 



0.02 



0.1 







3.0 

 3.9 









c. 



0.6 











Aug. 27. Sur- 

 face tempera-- 



1.2 







ture 21.5°. 









0.05 



. 













0.05 



r 









2.5 

 2.5 















0.05 



'D. 



Aug. 28. Sur- 





10.0 





0.15 



face tempera- -1 

 ture 21.2°. 









0.15 



































' 





















! 



! 



