1920] Allen: Plankton of the San Joaquin River 99 



July 19, being absent the rest of the year except for two small catches 

 in November. Maximum (1,481,088) in March. Recorded only five 

 times at other stations, mainly in March. 



Male eggs were recorded continuously at Station I for a short 

 time in February and March and there were occasional catches to 

 June 28. They were recorded once at Station II and twice at Station 

 III in small numbers. Both kinds were first recorded at Station I 

 on February 2. 



The maximum egg records of both kinds at Station I preceded the 

 maximum record for females of Filinia longiscta by three days and 

 the maximum for female eggs was almost reached again four days 

 after it. 



Unattached Filinia eggs were not certainly identified though 

 recorded. 



Filinia longiscta Ehrbg. 



Station I Station II Station III Daily Hourly 



Average 361,166 14,486 12,192 99,012 4,S61 



Identification positive. About twice as abundant at Stations II 

 and III as ever noted by Kofoid in Illinois and about fifty times as 

 many at Station I. Seasonal limitation earlier and more definite here 

 at all stations. Occurrence at Station I regular from January 5 to 

 July 19, missing thereafter except for two small catches in Decem- 

 ber. Maximum on March 8, 6,083,040. Catches of more than 1,000,- 

 000 taken seven times in February and March, three in May and one 

 each in June and July. An extremely important planktont at this 

 station. At Station II one small catch was made in January but the 

 regular occurrence began February 23, extending to April 13. Sev- 

 eral more catches to July 12, then none till late October, followed by 

 another in December. Maximum on March 8. At Station III one 

 small catch came in January, then the regular occurrence began on 

 February 8, extending with one lapse to July 12. Only two catches 

 thereafter, one in July and one in October. Maximum on June 28. 



There were rather distinct recurrent pulses at Station I culminat- 

 ing as follows: 



Jan. 15 Feb. 23 May 7 



Jan. 29. Mar. 8 June 3 



Feb. 12 Apr. 13 July 5 



Apr. 26 



Contrary to Illinois conditions the principal occurrence of this 

 form was below a temperature of 20° C. instead of above, and from 

 March to July instead of from May to October, so far as Station I is 



