238 









1896 1898 
Date | Tempers.) Hoof | Dees eee 
Mae: Ufone 42°" || 256° |) Mary i5iseae 46° 440 
Ta) Sen 40.7° | 610 | cole 9S Ale ood 480 
Ome 48.1° | 6,405 eo oe. 495° 240 
Apr dO). e ee 46.4° | 1,666 Are oSilee sameagace 200 
CME tee :) 66.82 Ap OTS | We ee ee 200 
CRY Siti 72° 1S MOMOL) Mee ano 56° 
SOC ERe 68° VS A004. «Dull eek! 2G ee Sy 800 
May yileoagc ee 68.8° 14,875 May? 35. <3 60° 
Bea Bee 76° 6,706 apa (Ove 62° 600 
Tee 72° 1,143 USE Aes 64° 35300 
25% ea he 753° 80 SO An ise 7,880 
| eos eae a 70° 5,040 
UNE. Ovenn oe 719° 320 | June 7.... oe 600 
a ig eae 73° 320 | caienarse 82:3 200 




and fungused individuals were also noted in these periods of decline. 
Males were recorded in September, December, and February. 
Chydorus is not given as a constituent of the plankton of Nor- 
wegian lakes by Huitfeldt-Kaas (98) or of Swiss lakes by Fuhrmann 
(’00), Amberg (’00), or Burckhardt (’00 and ’00a). Its absence 
from these cooler waters stands in sharp contrast with its abundance 
in warm and shallow European lakes. It is reported as abundant 
in Chroococcacee-rich lakes of North Germany by Apstein (’96), 
where it is acyclic, with larger development in April—October, and 
maximum in August or in May-June. According to Weismann 
(’79) Chydorus in some waters is polycyclic. It is also reported by 
Zacharias (’97a and ’98b) from the pond fauna of Trachenberg and 
many other German localities, where it forms “ein notorisches 
