DAPHNIA. • 95 



yet seen, being about the fifth of an inch in length, and 

 two hnes broad. Their motion through the water is pe- 

 cnhar, being a tumbhng, heavy sort of movement, and, 

 when seen in their native ponds, they seem to keep near 

 the bottom. When at the bottom of the vessel in w^hich 

 I kept them, I have frequently seen them turn head- 

 over-heels, throwing a regular summersault, ten or a 

 dozen times in succession. The males I have never yet 

 seen. 



The specimens I first procured from Bexley were mostly 

 all grievously infested with the wheel polypi, which had 

 settled in numbers upon all parts of the shell. I placed 

 them, however, when I reached home, in clear fresh water, 

 and shortly afterwards they moulted, or changed their 

 carapace, and thus got rid of their tormenting guests, 

 which afterwards, I have no doubt, became their food. 

 Previous to this change of carapace, the terminal spine 

 was very long, but I observed that in the new shell it 

 became shorter, and more obtuse. 



Hah. — Pond on Bexley Heath, Kent, August and 

 September, 1849. Pond at Norwood Green, Middlesex, 

 September 1849. 



4. Daphnia vetula. Tab. X, figs. 1, \a. 



Daphne vettjla, Midler, Zool. Dan. Prod., No. 2399, 1776. 

 Daphnia vetula, Strmis, Mem. Mus. Hist. Nat., v, t. 29, f. 25-6. 



— Baird, Auu. Mag. Nat. Hist., i, 255, t. 9, f. 13. 

 Daphnia sima, Midler, Entomostraca, 91, t. 12, f. 11-12, 1785. 



— LatreiUe, Hist. Nat. gen. et part. Crust., iv, 228. 



— Bosc, Hist. Nat. Crust., ii, 280. 



— Ramdohr, Beytr. zur Naturg., 18, t. 5-6. 



— Gruitlmisen, Nov. Act. Pliys. Med. Acad. Csesar. Nat. 



Cur., xiv, pt. 1, 399, t. 24, f. ]-6. 



— Desmarest, Consid. gen. Crust., 373. 



— Lamarck, Hist. An. s. Vert., v, 182. 



— M. Edwards, Hist. Nat. Crust., iii, 382. 



— Koch, Deutsch. Crust., h. xxxv, t. 12. 



