229 
part in the seasonal delimitation of the amplitude of Bosmina pulses. 
The Bosmina population in the plankton consists largely of 
parthenogenetic females. Males and females with ephippial eggs, 
were recorded only in October-December, 1897, and then only in 
small numbers and isolated occurrences. Females with eggs or 
embryos and the free young were found at all seasons of the year and 
at all temperatures, but most abundantly at the time of the pulses. 
Parasitized or fungused individuals are also found occasionally at 
these seasons of greatest numbers, and the high mortality following 
a pulse is evidenced by the large number of dead occurring in the 
plankton. The proportions of females, females with eggs or em- 
bryos, young, and dead during the May—June:pulse of 1898, may 
be traced in the following records. 
BosMINA PER M.3, May—JuNE, 1898. 
Date Females ase Young | Total living Dead 
LN ongy Wa eye Cee 800 0) O 800 6) 
May 3. ois... 1,600 — 400 800 2,800 0 
ts Sal Oar 1,600 1,000 1,000 3,600 400 
Pe LY ate 1,300 1,100 1,100 3000 100 
US 0 LLNAY gegen 3,280 1,400 1,240 5,920 920 
ie) oo)! Dares PS) PAO) 2,000 6,800 33,920 1,280 
Ne seit aae 38 , 800 9,200 14,800 62 , 800 9,200 
cha A esl eu erase 2,200 3,000 800 6,000 1,400 
ine Zit eee ss 1,000 500 0) 1,500 100 
Gm Ok 2 Otaer eta aits./e 300 200 200 700 100 
Bosmina longirostris has been frequently reported in the plankton 
of European lakes. Apstein (’96) finds it perennial in Plonersee 
with larger numbers in June-September and a maximum in July. 
No pulse-like recurrence is noted, parthenogenesis prevails, and 
males and ephippia are rare. His results, save in the matter of 
pulses, are thus in general accord with ours. Stingelin (’97) notes 
