FAUNA OF THE CHESS AND GADE. 345 



only to those collections for which my rough notes give informa- 

 tion about variations in the specimens. 



On April 8th, 1913, numerous specimens of C. viridis were 

 taken from Chipperfielcl Common Pool. Many of them had 

 ovisacs ; they were very much the same in size, viz., about 

 =1% inch in total length. The antennae varied in length, being a 

 little shorter than the first segment in some, and as long as that 

 segment in a few of the specimens. The lateral bristle of the 

 furcal segments was situated decidedly farther forward than it is 

 in the gigas forms, and in one specimen the innermost tail-setae 

 were not much longer than the outermost. 



The length of the furcal segment in C. viridis is subject to 

 great variation, but the greatest difference in this respect was 

 noted among a few specimens taken from Langleybury Pool on 

 November 20th, 1915. In some of these the length was more 

 than three times that of the last abdominal segment. 



The colours of specimens taken in the country of the Chess 

 and Gade were dull green or brown, the ovisacs being usually 

 dark green or brown, but occasionally light green or sandy. 



Males have been found on many occasions, but they seem to 

 be more numerous during the winter months. They were more 

 slender and graceful than the females, with strongly hinged 

 antennae, and usually of a red colour. On January 27th, 1916, 

 several water samples from Langleybury Pool yielded one male 

 for every four females, and, on February 3rd, 1916, the water 

 samples from the deeper parts of the same pool yielded com- 

 paratively few adult specimens of both sexes but several thousands 

 of immature specimens, all of a red colour, in the Nauplius and 

 Copepod stages. 



Of C. viridis, var. gigas, I have very many records. In many 

 cases they have been taken together with specimens of the normal 

 type, but many of the rough notes record specimens of gigas 

 without any reference to the normal type. Large numbers, with 

 ovisacs, have occurred in the months of March, May, June, July, 

 and October, while fewer specimens have been obtained in the other 

 months of the year. The localities yielding specimens of gigas 

 are also numerous, the chief being, roughly in descending order, 

 Berkhamsted Castle Moats, Parsonage Farm Pool, Frithesden 

 Pool, the Gade at several parts between Great Gaddesden and 



