260 HYDRACHNA. 



away by each, when its existence quickly terminated ; the stronger, 

 meantime, either pursuing an uninterrupted course, resting on some 

 neighbouring substance, or lying supine at the bottom, while more lei- 

 surely devouring its prey. 



Young Hydrachnae also ferociously seize the animals, though larger 

 than themselves ; thence, where a few minute Daphnioe escaped at first, 

 as in the preceding case, they too were quickly devoted to destruction. 



Thus, Hydrachnae do not spare each other ; so that whether impelled 

 by hunger or excited by animosity, numerous colonies of both them- 

 selves and the Daphnia are gradually exterminated, with exception of a 

 single specimen remaining, the ultimate victor of both. 



A small specimen fixed itself on the Hydrachna extendens, a com- 

 mon scarlet flattened kind, already referred to as larger, and named by 

 Miiller ; nor could the victim by any means dislodge the assailant. It 

 lay as if stunned and about to perish, until relieved of its enemy. This 

 red species is one of the quieter and more pacific. From frequenting 

 sandy places, and moving heavily, it is liable to pursuit. Sometimes the 

 animals of one species are attacked and devoured by the Hydrachna of 

 another, not a tnird of the size. 



These mutual attacks are accompanied by ah 1 the ferocity of the 

 fiercest animals of prey, and they are effected by means of their offen- 

 sive organs reciprocally. Great devastation is the consequence. The 

 formidable fangs of a beautiful black and yellow species, with bluish legs, 

 are seen from a specimen of the character of Plate LXIX., fig. 27 ; also 

 from the Hydrachna, figs. 25, 26, which was taken in May, in Braid 

 Hills pond. 



Hydrachnae continue plump and sleek, from feeding on those dying 

 in their vicinity. The colour of some named here, the e<rtendens, for 

 example, remained vivid, and the body in good condition, while surviv- 

 ing others : and if one of the dead was pierced, the substance escaping 

 tinged a considerable quantity of water red. 



The disposition of these little animals, so strongly displayed in more 

 violent sensations, is greatly modified. From four specimens of them 



