Insects. 



193 



Notes on British Entomostraca. By W. Baird, Esq., M.D., &c. &c. 



Daphnia brachiata. 



The minute crustaceoiis insects which were arranged by Muller 

 under the general name of Entomostraca, meaning insects inclosed 

 within a shell, have met with very little attention from the naturalists 

 of Great Britain. Their exceeding minuteness and extreme delicacy 

 of structure, have perhaps been the causes of this neglect, deterring 

 most naturalists from examining them and studying them as they re- 

 quire to be studied — fresh from their native habitats. The difficulty 

 of preserving them obliges the naturalist to seek them in their secret 

 lurking-places — the fresh-water ponds and ditches, and the little pools 

 in the rocks on the sea-shore, where they are chiefly to be found, and 

 to study them as it were on the spot, with the aid of his microscope. 

 The celebrated Latreille, after some remarks upon this extremely in- 

 teresting class of little creatures, observes, " The organs of mastica- 

 tion are almost to this day hid from the eyes of observers. How can 

 we discover a part which does not constitute the tenth part of a mi- 

 croscopic animal ? The eyes of De Geer and Jurine however have 

 believed that they could distinguish something. The latter has re- 

 marked, in the Monocle puce of Linnaeus, two mandibles without 

 teeth &c. These observations are so delicate, that out of a hundred 

 entomologists, scarcely shall we find two or three who are able to re- 

 peat them, and participate, in some sort, in the pleasures of that dis- 

 covery."* Since Latreille penned the above, our knowledge of the 

 anatomical structure of these marvellously small creatures has been 

 much extended, and the few naturalists who have had patience to re- 

 peat the observations alluded to in the above quotation, have, I am 

 sure, fully participated in the pleasures enjoyed by the first disco ver- 



* ' Hist. Gen. ct Part, des Crustac. et Insect.' iv. 109. 



