140 CRUSTACEA. 



appearing to form a third to the second and following feet, as far as 

 the tenth pair. In proportion as these organs diminish in size, the 

 leaflets approximate more closely, the forceps is more clearly defined 

 and less pointed, and the first toe becomes wider, shorter and rounder. 

 The two anterior feet, which are much larger and are formed like 

 oars, resemble ramous antennae, and have been considered as such 

 by some writers(l): they exhibit four multi-articulated setaceous 

 threads, the two last joints, one of them particularly, being much 

 longer than the others which are situated on the internal side or 

 anteriorly. The two at the extremity are evidently analogous to the 

 toes of the forceps, the remaining two also correspond to as many of 

 the lateral leaflets; it is easy to convince ourselves of this by com- 

 paring these parts in young specimens. After their sixth or seventh 

 change of tegument, the two or three following feet of the latter 

 greatly resemble the two anterior ones, and even their antennae are 

 longer in proportion than in the adult, and are terminated by setae or 

 hairs. The eleventh pair are very remarkable(2). The first joint, 

 behind the vesicles, presents two circular valves, laid one on the 

 other, formed by two leaflets, and containing the ova, which resem- 

 ble granules of a bright red colour. Every specimen which has 

 hitherto been examined being always found to possess this kind of 

 feet, they have been considered as hermaphrodites, and are consi- 

 dered capable of self- impregnation. 



These animals inhabit ditches, pools, stagnant waters, &c. and usu- 

 ally in myriads. Abducted, when thus assembled, by violent winds, 

 they have been seen to descend in rain. They generally make their 

 appearance in spring, and in the beginning of summer. Their cus- 

 tomary food is the Tadpole. They swim well on their back, and 

 when they sink into the mud they erect their tail. When first pro- 

 duced they have but one eye and four feet, resembling arms or oars, 

 furnished with tufts of hairs, the second of which are the largest. 

 Their remaining organs are regularly developed after each change 

 of tegument. M. Valenciennes, an attache of the Mus. d'Hist. Nat. 

 has remarked that these Crustacea are frequently devoured by the 

 bird vulgarly called the Lavandiere(3). 



The number of species known being very small, it is unne- 



(1) They also seem to represent the two first foot-jaws. 



(2) SchsefFer distinguishes them by the name of uterine feet. The preceding 

 nine pairs, according to his phraseology, form forceps, those of the first oars, or 

 true feet; finally, those which follow the uteruie feet, or the twelftli pair and fol- 

 lowing ones, branchial feet. The vesicular sacs lengthen and lessen just as gra- 

 dually; their use is unknown. 



(3) The Motacilla alba, and cinerea, L. Am. Ed. 



