TETRA DEC A PODS. 



305 



form, the change being induced by the greater or less saltness 

 of the water. Artemia produces young by budding (parthe- 

 nogenesis) as well as from eggs. 

 A species observed near Odessa 

 produced females alone in warm 

 weather; and only in water of rf 

 medium strength were males 

 produced. The eggs of Arte- 

 mia fertilis have been sent in 

 moist mud from Utah to Mu- 

 nich, Germany, and specimens 

 raised from the eggs by Siebold, 

 proving the great vitality of the 

 eggs of these Phyllopods, a fact 

 paralleled by the similar vitality 

 of the eggs of the king-crab. 

 Fig. 249 b represents the Nau- 

 plius of the European brine- 

 shrimp. 



Order 4. Tetradecapoda. 

 To this order belong the sow- 

 bugs (Isopoda) and the beach- 

 fleas (Amphipoda). In these 

 Crustacea there is no cephalo- 

 thorax, but the head is small, After Verrffl.' 

 bearing two pairs of antennae, and a pair of jaws, and three 

 pairs of maxillae. The thorax is continuous with the abdo- 

 men. Eespiration is performed by lamellate or leaf -like 

 gills on the middle feet in the Amphipods, or on the hinder 



abdominal feet in 

 the Isopods. The 

 lowest Isopods are 

 parasitic, they 

 graduate into the 

 Amphipods, and 

 the higher Amphipods are connected with the shrimps (De- 

 capoda) through a group (probably a suborder) of synthetic 

 forms (Palceocaris, Acanthotelson and Gampsonyx, Fig. 

 254) such as are found in the coal formation of Illinois 



Fig. 252. Brine - shrimp, Artemia 

 gracilis, enlarged, a, first antenna ; b. 



Fig. 253. Artemia fertilis from 

 egg-sac ; c, male claspers. 



Great Salt Lake, e, 



