History of British Entomostraca. 321 



ject.* That he is wrong cannot be doubted, I imagine, and there 

 is every reason to presume, that their being carnivorous serves a 

 most useful purpose in the economy of nature. The adults in their 

 turn fall victims to, and are devoured by, other insects, the chief of 

 which are the Hydrachnse, Hydrae, and larvae of aquatic insects, 

 which destroy them in such vast numbers;, as in some measure to 

 counterbalance the most extraordinary fertility which they possess, 

 and which I have already mentioned above. 



Species. 

 A. Fresh Water Species. 

 1. Cyclops quadricornis — Plate VIII. Fig. 1,1-14 Specific character — An- 



tennis longis ; corpore ovato ; cauda recta bifurcata ; furca. utraque setis 



quatuor plumosis instructs, ; ovariis externis duobus. 

 Synonimes, Sfc Cyclops vulgaris, Desmarest, Considerat. generates sur les 



Crustaces, p. 362. 

 Monoculus quadricornis, Jurine, Hist, des Monoc., &c. 1820, pp. 1-49. 



Plates 1, 2, 3. — Figures excellent. 

 Cyclops quadricornis — Ramdohr, Beyt. zur Naturg. einigen deutschen Monoc- 



arten, 1805. Pp. 1-6, t. 1, fig. 1-10 ; t. 2, f. 1, 8. 

 Cyclops quadricornis — Mutter, Entomostraca, &c. p. 109, tab. 18, fig. 1-4, 



1785 Figure pretty good. 



Nauplius saltatorius, (the young in its first state,) Mutter, Entomost. p. 40, 



tab. 1. fig. 3-7. 

 Eichhorn, Beytrage zur Naturgeschichte dar Kleinsten Wassertbiere, p. 54, 



tab. 5, fig. m. n. 1781 — Very bad figure. 

 Le Monocle a quatre comes, De Geer, Memoires pour servir a l'bistoire des 



insectes, torn. 7, p. 483, plate 29, fig. 11-12, (adult insect,) plate 30, fig. 



5-9, (egg and young,) 1778. — Figures not quite correct. 

 Monoculus quadricornis, Fabricius, Systema Entomologias, p. 295, 1775. 

 Der Naturforscber, Stuck 5, p. 247, 1775. 

 Neue Mannigfaltigkeiten, i. p. 640, fig. 3, 1774 — Figure apparently copied 



from Roesel. 

 Le Monocle a queue fourchue, Geoffroy, Hist, abreg. des Insectes, Vol. ii. 



p. 656, No. 3, plate 21, fig. 5, 1764.-^4 very bad figure. 

 Pediculus aquaticus, Baker, Employm. for Microsc. p. 383, pi. 15. fig. 1-4. 



1764.* 

 Monoculus quadricornis, Scopoli, Entomologia Carniolica, p. 413-1139, 



1763. 

 Monoculus Apus, Poda, Insecta Musei Grascensis, p. 125, tab. 1. fig. 11, 12, 



1761. f 



* Geoffroy also says, that all the Monoculi live upon vegetable matter alone. 

 — Hist, abreg. des Insect. Vol. ii. p. 654. 



f Baker's correspondent complains sadly of the figures which Leeuwenhoek 

 gives, as being very incorrect, and yet the figures which he gives are ten times 

 worse than Leeuwenhoek's ! ! 



\ The name of Mon. Apus is given incorrectly by Poda, as his figure, though 

 very indifferent, is clearly that of the C. quadricornis. 



