T-KTltA DECAPODS. 



285 



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

 of the water. Art cm in 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 

 medium strengtn were males 

 produced. The eggs of Arte- 

 mia fer tills 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. 244 b represents the Nau- 

 plins of the European brine- 

 shrimp. 



Order 4. Edriophtltalma. 

 To this order belong the sow- 

 bugs (Tsopoda) and the beach- 

 fleas (Alltplupoda). In these ^ rac i &) enlarged ., first antenna; 6, 

 Pvnaf'ipp'i thorp i<? Tin PPlYh-iln- second antenna or chtsper ; c, stalked 



eye : rf, e, jaws ; /, a foot ; g, egg-sac. 



thorax, but the head is small, After Verriii. 

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

 pairs of maxilla?. The thorax is continuous with the abdo- 

 men. Kespiration 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 



Tig.248.Arfemiaferlilifi from Great Salt Lake, e, rrrnduite into the 

 egg-sac ; c, male clampers. 



Amphipods, and 



the higher Amphipods are connected with the shrimps (De- 

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

 forms (P'alwocaris, Acanthotehon and Gampsonyx, Fig. 

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



Fig. 247. Brine- shrimp, 

 gracuis, enlarged. 



ci nia 



