FAUNA OF THE CHESS AND GADE. 419 



enough to suit the rotifer Hydatina senta ; and the localities 

 above-mentioned, where C. serrulatus thrives, vary much with 

 respect to depth of water and exposure to sun and wind. They 

 all agree in having a muddy bottom or masses of Conferva or 

 other small aquatic plants in which the Copepod can readily 

 burrow and take refuge. C. serrulatus seems to be very prone 

 to burrow into mud and masses of small aquatic plants when it 

 is disturbed, and this habit I have repeatedly observed when 

 examining the various water samples containing this Copepod ; 

 on some occasions, in fact, a few specimens have in this way 

 escaped capture for some time. It seems that the presence of a 

 muddy bottom, or of Conferva or other small aquatic plants, or 

 of floating leaves fallen from adjacent trees is especially favour- 

 able to the presence of large numbers of C. serrulatus. 



Bedmond Pool, which has always given very poor results, 

 rarely presents any of these features. As far as it can be 

 examined from the sides, its bed, which sinks rapidly towards 

 the centre where its depth is said to be over twelve feet, is 

 almost everywhere clean and stony. The poor results obtained 

 from Chesham Eoad Pool cannot be due to absence of mud, and, 

 in some parts, there is no want of aquatic plants to serve as 

 cover, so that I have been at a loss to understand why more 

 specimens have not been obtained. Examination of the habits 

 of another species of Cyclops, of which a moderately large 

 number of specimens have been obtained from the pool, seems 

 to suggest one cause. I refer to Cyclops fuscus, Jurine, a 

 stoutly built and aggressive Copepod. Many times I have seen 

 individuals of this species attack others, especially specimens of 

 C. serrulatus, with great energy, and ova-bearing females in 

 particular have been left lifeless, or nearly so, after these attacks. 

 The numbers of C. serrulatus are no doubt also kept down (and 

 so also those of C. fuscus) by the Sticklebacks which are also 

 found in the pool. It may be mentioned that these fishes are 

 also found in Bedmond Pool, which also gives poor yields of 

 Copepods, and these pools of Chesham Eoad and Bedmond are 

 two of the few pools, altogether unconnected with the streams or 

 the canal, which contain Sticklebacks. 



3. The occurrence of ova-bearing females. — These have been 

 obtained in every month of the year except November. The 



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