INTRODUCTION. 7 



" for," says Miiller, " tliey seize hold of them while 

 swimming, by their feet, and daintily suck the life's blood 

 out of their captives with their sharp beaks,"* " The 

 Hydrgef also, and not a few aquatic larva), lay snares for 

 them, and many Vorticellse frequently grievously infest 

 them, for they not only adhere, often in heaps, to the mem- 

 bers projecting beyond the shell, but also, nestling them- 

 selves within the shell, they overspread the whole body 

 with their own colonies, not a little retarding the motion 

 and agility of their host."| The larva of the Corethra 

 plumiconiis, known to microscopical observers as the 

 skeleton larva, is exceedingly rapacious, more especially of 

 the Daphni^. They seize their prey with the rapacity of 

 a pike, grasping it with its two strong jaws, and gorging 

 them alive. § Pritchard says they are the choice food of a 

 species of Nais, which he calls the Lurco, and which de- 

 vours them in great numbers. || The Chydorm sphericus 

 is their especial favorite, and I have repeatedly verified 

 Pritchard's observations, having counted at least ten in- 

 dividuals swallowed alive, and lodged in the different 

 stomachs of this glutton. Those in the first and second 

 stomachs were still alive, while those contained in the in- 



* Entomost. p. S. 



f "It would appear that there is something eminently poisonous to 

 animals in the fresh-water Hydrte. ' I have sometimes,' says Baker, ' forced 

 a worm from a polype the instant it has been bitten (at the expense of 

 breaking off the polype's arms), and have always observed it die very soon 

 afterwards, witliout one single instance of recovery.' To the Entomostraca, 

 liowever, its touch is not equally fatal , for I have repeatedly seen Cyprides 

 and Daphnia;, entangled in the tentaeula and arrested for some considerable 

 time, escape even from the very lips of the mouth and swim about after- 

 wards unharmed — their shell evidently protecting them from the poisonous 

 excretion." — Johnston, Brit. Zooph., 2d edit., p. 181. 



X Loc. cit., p. 8. They are frequently covered completely with a small polype, 

 called by M. Reamur " Polypes a bouquet ;" for an account of which sec 

 Trembley's ' Memoire sur les Polypes a bouquet, a la suite des decouvertes 

 de Needham,' Leyde, 17^7 ; also De Gccr, ' Hist, des Ins.,' vii, 437, where 

 he informs us that in Api-il 1742 lie first observed this fact, and made a re- 

 port upon it to the Academy of Sweden, which that learned body inserted 

 in the Memoirs of tlie Academy in 1747, previously to Mr. Trembley's work 

 being published. 



§ Brightwcll, Zool. Journ., v, 39G ; and t. xix, f. 1. 



II Microscop. Cabinet, p. SI. 



