HYDRACHNA. 259 



enlarged. Tlie natural prey of this latter is the Hydrachna spinifer. — 

 Figs. 3, 4, 5. 



On the margin of this pond lay the fragments of a decajdng boat, 

 containing a quantity of macerating leaves fallen from the neighbouring 

 plantations among ten or twelve gallons of water, where had also gene- 

 rated numerous broods of the lower animals — the boat having remained 

 two or three years in the same spot undisturbed. 



The water was replete with multitudes of the Entomostraca in par- 

 ticular, in considerable variety, and among them the finest specimens of 

 the Daphnia, or Water Flea, which is one of the largest of the tribe, nor 

 much inferior to the smaller Hydrachnae. 



I was accustomed to resort thither for supplies of microscopic objects, 

 both in general and promiscuous collections, and as selected objects from 

 among many, being the most valuable to be obtained in the neighbourhood. 

 On one occasion I found that a phial of miscellaneous matter had in- 

 cluded above sixty Daphniag, and six specimens of the Hydrachna ferojc ; 

 these being put aside for the night, without farther expectation of what 

 the morning might disclose. I observed, on the return of light, with 

 some surprise, that each Hydrachna had seized a Daphnia — hurrying it 

 along, though hardly to be retained from strength and dimensions within 

 its ferocious grasp ; and on the following morning, that not one of the 

 sixty, unless a few minute specimens, survived — the shells of the rest, all 

 lying at the bottom of the phial, voided of their contents, testified the 

 fate of their recent tenants. 



Again, ten of the same, the first species of the Hydrachna above 

 named, having been accidentally committed to a jar, with above a hun- 

 dred Daphnige, none of the latter had escaped next day. 



As it was impossible that the assailants required such a quantity of 

 food, it became evident that the victims were the objects of a mere wan- 

 ton thirst for destruction — a most mischievous feature in the history of 

 these minute carnivorous animals. 



It was discovered, besides, that among a number of the Entomostraca 

 introduced along with the Hydrachna, one was speedily seized, and borne 



