188 



BRACHIONUS PALA, TYPE FORM. SEXUAL CYCLE. 



* Includes free eggs of other varieties also. 



culmination of a pulse is very large. For example, the sudden ver- 

 nal pulse of 716,982 on April 24 is accompanied by 28,584 free 

 winter eggs. The pulse declines to 22,224 on April 29, and the free 

 winter eggs rise to 95,841, and the empty loricas to 26,114. 



Females carry 1-5 summer eggs, and 1-8, or even more, male 

 eggs. There is great variation in the size of the summer eggs, these 

 and -the male eggs appearing almost to intergrade. 



Brachionus pala, including B. amphiceros, is a common constitu- 

 ent of the plankton of shallow warm waters. It has not been 

 reported from the larger and cooler lake waters by Apstein ('96), 

 Burckhardt ('00 and 'OOa), or Jennings ('94, '96, and '00). Zacha- 

 rias ('98) and Marsson ('00) find it in the summer plankton of 

 smaller lakes and ponds in Germany. Seligo ( '00) records it from 

 April to October, with a maximum in August, in Prussian lakes ; and 

 Lauterborn ( '98a) finds it to be perennial and polycyclic in -the 

 Rhine. Schorler ('00) reports both pala and amphiceros from the 

 Elbe, the former being abundant in May and sporadic during the 

 summer, while the latter was abundant in April, June, and Septem- 

 ber, and rare at other times during the warmer months. Zimmer 



