BRANCHIOPODA. CLADOCERA. 381 



saddle-shaped area, the cuticle acquiring a firm consistency 

 and brown colour. At the next moult after the eggs have 

 entered the brood-pouch, they are contained in the shed cuticle, 

 the bivalved thickened region or ephippium remaining as a 

 protective case for the eggs after the rest of the cuticle has 

 disintegrated. 



The Cladocera live for the most part in fresh water, and 

 certain species inhabit deep inland lakes. Others live in 

 brackish water and the sea. They swim quickly, and usually 

 with a jumping movement. Some of them attach themselves 

 to fixed objects by means of the dorsal " cervical gland " (p. 372). 

 When the body is thus fixed, the swimming feet are able by 

 their rhythmic movements to set up currents in which small 

 food particles are swept towards the animal. 



Fam. 1. Sididae. Heart elongated. Gut straight. t> pairs of similar 

 lamellate legs, with well developed epipodites. Latona Straus, Daphnella 

 Baird, Penilia Dana, Limnosida Sars, Sida Straus, with large cervical 

 adhering apparatus. Holopedium Zadd. , 2nd antennae unbranched. 



Fam. 2 and 3. Daphnidae and Lynceidae. Heart shortly oval, gut 

 with a direct course in Daphnidae, coiled in Lynceidae ; 5 or pairs of 

 limbs, the lamellar character and the branchial appendages becoming 

 more developed from before backwards. (Daplmidae) llyocryptus Sars, 

 Acantholeberis Lilljeb. ; Bosmina Baird, anterior antennae long, a sixth 

 (rudimentary) pair of legs is present ; Drepanothrix Sars, Macrothrix 

 Baird, Lathonura Lilljeb. ; Mo'ina Baird, anterior antennae large and 

 prehensile in the $ of M. paradoxa : Scapholeberis Schodl., Ceriodaphnia 

 Dana, Simocephalus Schodl. ; Daphnia Mull., the head shield not separated 

 from the shell by a groove (Fig. 251). (Lynceidae) Eurycercus Baird, 

 with 6 pairs of legs, Camptocercus Baird, Acroperus Baird, Alonopsis 

 Sars, Alona Baird, Phrixura Mtill., Pleuroxus Baird, Chydorus Leach, 

 Monopsilus Sars. 



Fam. 4. Polyphemidae. The shell does not enclose the body and legs 

 as in the other families of the Cladocera, but is small and usually only 

 contains the brood chamber. Head bluntly rounded, with very large 

 compound eyes. Legs slender, distinctly jointed, branchial appendages 

 rudimentary. Marine and freshwater. Podon Lilljeb. and Evadne 

 Loven with 4 pairs of short legs crowded together. Abdomen rudi- 

 mentary, covered by the shell. Polyphemus Mull, and Bythotrephes 

 Lilljeb. The second antennae, four pairs of legs, and the abdomen are 

 much elongated. The legs with rudimentary branchial appendages. 

 Leptodora Lilljeb. The head and posterior part of the body elongated 

 and the latter distinctly segmented. The 6 pairs of cylindrical \mbranched 

 legs on the contrary are crowded together, the anterior pair being long. 

 1st antennae long and comb-like (sensory) in the J , 2nd antenna large, 

 with stout basal joints. The summer eggs develop directly in the brood- 

 pouch into the form of the adult, but the (fertilized) winter eggs hatch 

 out as nauplius larvae. Fr. w. lakes of N. Europe. 



