278 
the warmer season, on the other hand, the pulses frequently attain 
100,000 or over. 
The maximum record of 928,984 was made in the stable low 
water of June 19, 1895. All large developments thus lie at tem- 
peratures above 70°. 
The nauplii bear much the same relation to hydrographic condi- 
tions as that found in the adults; for example, in Cyclops viridts. 
This is seen in the fact that in unstable years such as 1896 and 1898 
the numbers are on the average only 28 and 68 per cent. of what 
they were in the more stable conditions of 1895 and 1897, and the 
average monthly population in July-December in the unstable 
conditions of 1898 is only 18 per cent. of that in the same months 
of the previous year. 
The relative numbers of adult, young, and larval stages of the 
Cyclopide are given in the accompanying table. 


Nauplii Young Cyclops Adult Cyclops 







Year 
No. | Ratio No. Ratio No. Ratio 
| 
1804) A) ce. 456,483 | 38 59,598 5 11,726 1 
LE OSHS See DAN ps ero 680,749 | 5 140,779 1 
1S OGR ae ete 145 524 | 17 428,211 | 5 84,786 1 
TSOUR. eee. ae 1,828,720| 18 545,200 | 5 LOPES Owl ed 
MSO See 1,908,780 30 248,576 4 62,735 1 
SOO ean oe eee 121,345 | 61 5,422 3 
Totals....| 8,508,570 / 2 | 1,967,756 5 | 404,749; 1 



The ratios between total adult and young, 1 to 5, are fairly 
constant in the different years, falling to 1 to 3 in January—March, 
1899, and to 1 to 4 in 1898,—a year in which the colder part of the 
year was most fully represented. This ratio probably represents 
more truly the relationship of young and adult in the total yearly 
production. The ratios of adults to nauplii in the several years 
vary considerably from the totals of all years (1 to 21), rising to 1 to 
