DAPHNIA. 
95 
yet seen, being about the fifth of an inch in length, and 
two lines broad. Their motion through the water is pe- 
culiar, being a tumbling, 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 which 
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. 
Hab . — Pond on Bexley Heath, Kent, August and 
September, 1849. Pond at Norwood Green, Middlesex, 
September 1849. 
4. Daphnia vetula. Tab. X, figs. 1, la. 
Daphne vetula, Muller , Zool. Dan. Prod., No. 2399, 1776. 
Daphnia vetula, Straus, Mem. Mns. Hist. Nat., v, t. 29, f. 25-6. 
— Baird, Ann. Mag. Nat. Hist., i, 255, t. 9, f. 18. 
Daphnia sima, Muller, Entomostraca, 91, t. 12, f. 11-12, 1785. 
— Latreille, Hist. Nat. gen. et part. Crust., iv, 228. 
— Bose , Hist. Nat. Crust., ii, 280. 
— Ramdohr, Beytr. zur Naturg., 18, t. 5-6. 
— Gruithuisen, Nov. Act. Phys. 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. Bdwards, Hist. Nat. Crust., iii, 382. 
— Koch, Deutsch. Crust., h. xxxv, t. 12. 
