ENTOMOSTRACA I CYCLOPS ; DAPHNIA ; APUS. 641 



collected by the Tow-net. The body of the Cyclops is soft and gela- 

 tinous, and it is composed of two distinct parts, a Thorax (Fig. 331, a) 

 and an Abdomen (6), of which the latter, being comparatively slender, 

 is commonly considered as a tail, though traversed by the Intestine 

 which terminates near its extremity. The Head, which coalesces 

 with the Thorax, bears one very large pair of Antennae (c) possess- 

 ing numerous articulations, and furnished with bristly appendages, 

 and another small pair (d) ; it is also furnished with a pair of 

 Mandibles or true jaws, and with two pairs of 'Feet-jaws,' of which 

 the hinder pair is the longer and most abundantly supplied with 

 bristles. The Legs (e) are all beset with plumose tufts, as is also 

 the Tail (/, /) which is borne at the extremity of the abdomen. 

 On either side of the Abdomen of the female, there is often to be 

 seen an Egg-capsule or external Ovarium (b) ; within which the 

 Ova, after being fertilized, undergo the earlier stages of their de- 

 velopment. — The Cyclops is a very active creature, and strikes the 

 water in swimming, not merely with its Legs and Tail, but also 

 with its Antennae. The rapidly-repeated movements of its Feet- 

 jaws serve to create a whirlpool in the surrounding water, by 

 which minute animals of various kinds, and even its own young, 

 are brought to its mouth to be devoured. 



500. The tribe of Branchiopoda also is divided into two Orders 

 of which the Cladocera present the nearest approach to the pre- 

 ceding, having a Bivalve Carapace, no more than from four to six 

 pairs of Legs, two pairs of Antennae, of which one is large and 

 branched and adapted for swimming, and a single Eye. The com- 

 monest form of this is the Daphnia pxdex, sometimes called the 

 ' Arborescent Water-Flea ' from the branching form of its Antenna?. 

 It is very abundant in many ponds and ditches, coming to the sur- 

 face in the mornings and evenings and in cloudy weather, but 

 seeking the depths of the water during the heat of the day. It 

 swims by taking short springs ; and feeds on minute particles of 

 Vegetable substances, not, however, rejecting Animal matter when 

 offered. Some of the peculiar phenomena of its Reproduction will 

 be presently described (§ 503). 



501. The other Order, Phyllopoda, includes those Branchiopoda 

 whose body is divided into a great number of segments, nearly all 

 of which are furnished with leaf -like members, or ' fin-feet.' The 

 two Families which this order includes, however, differ considerably 

 in their conformation ; for in that of which the genera Apus and 

 Nebalia are representatives, the body is enclosed in a Shell, either 

 shield -like or bivalve, and the feet are generally very numerous ; 

 whilst in that which contains Branchipus and Artemia, the body 

 is entirely unprotected, and the number of pairs of feet does not 

 exceed eleven. The Apus cancriformis, which is an animal of 

 comparatively large size, its entire length being about 2j inches, 

 is an inhabitant of stagnant waters ; but although occasionally very 

 abundant in particular pools or ditches, it is not to be met-with 



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