90 INTUODUCTION TO ZOOLOGY. 



giant, for the mother has been seen to devour her own young. 

 Jurine, while he admits the fact, urges, in vindication of his 

 little favourites, that she does not do so from choice, hut 

 that the helpless young cannot resist the action of the 

 whirlpool the mother causes around her, and are thus car- 

 ried unconsciously into the old one's mouth. 



Another one-eyed Crustacean deserves mention for the ex- 

 hibition it affords of one of those striking instances of provi- 

 dential care which the little, no less than the great, experience 

 from the Maker of all. In drains and ditches there is found 

 in abundance a minute creature, which, from its branching 

 horns (antennce), and its peculiar movements, is called the 

 arborescent water-flea (Daphnia pulex). It looks like a small 

 crustaceous animal enclosed in a transparent bivalve shell. 

 The eggs are developed in the space between the body of the 

 animal and the shell. The Daphne continues its moultings 

 even when full grown, but perishes with the cold of winter. 

 Ere that season, however, comes on, two eggs are produced, 

 enclosed in a horny case, and are thrown off with the shell. 

 These float on the water, protected from injury by their pecu- 

 liar covering, and from these the numerous progeny of the 

 ensuing summer is derived. ISTor is this all; the impregnated 

 female is not only fertile for her own life, but conveys that 

 fertility to her female offspring for five or six successive 

 generations, whether they be derived from the ordinary 

 eggs or from those enveloped in the horny covering.* 



It is obvious, from the particulars we have stated, that 

 the Crustacea afford matter for curious inquiry and patient 

 investigation, whether sought for 



" By paved fountain or by rushy brook, 

 Or on the beached margin of the sea." 



But it will be exhibiting them in a different light, if we men- 

 tion to our readers a species that attacks the works of man, 

 and crumbles into dust the wood-work of his piles and flood- 

 gates, piers, or jetties, constructed in salt-water. It is the 

 Limnoria terebrans^ a pigmy assailant, scarcely more than 



* See note in preceding page. 



f Kirby and Spence's Entomology, vol. i.; W. Thompson, in Edinburgh 

 New Phil. Journal, January, 1835. Another species, C/ielura terebrans 

 has been recorded as native by Dr. Allmann, in Annals of Nat. Hist. 

 June, 1847; and so'ric further particulars are given by Mr. Thompson in 

 the same periodical for Sept. 1847. 



