448 



CRUSTACEA MALACOSTRACA. 



Isopoda) a well- 

 marked stage with 

 two pairs of an- 

 tennae and man- 

 dibles, followed by 

 the shedding of a 

 larval cuticle, has 

 been recognized in 

 the development of 

 the egg as corre- 

 sponding to the 

 nauplius larva of 

 other Crus t a c e a. 

 (Compare the cor- 

 responding stage in 

 the development of 

 the fresh -water 

 crayfish, Fig. 282.) 

 In the remaining 

 Malacostraca, i.e., 

 in the Euphausiid 



Schizopods, in Stomatopods and Decapods (for the development 



of the Syncarida see p. 462) a metamorphosis presenting varying 



degrees of completeness is nearly always found in the life- history. 

 Compared with the gradual series of stages which in the 



Phyllopod Branchiopods and most Copepods leads from the 



nauplius larva to the adult condition, the metamorphosis of 



the Malacostraca is 



characterized by some- 



what abrupt transi- 



tions from one larval 



stage to another, and 



by the introduction of 



stages which are not 



in the direct line lead- 



ing to the adult form. 



" The metamorphosis 



Of the lower Crustacea 

 Koavc flip <samp 



FIG. 282. Embryo of Astacus flumatiUs in the nauplius 

 stage. A (above) rudiment of eye ; a', a" first and second 

 antenna ; G cerebral ganglion ; gav ganglion of the second 

 antenna ; gm ganglion of the mandible ; I upper lip ; 

 m mandible ; TA thoraco-abdominal rudiment ; A (lying 

 in TA) anus (from Lang, after Reichenbach). 



A 



A 



fn flint f\f 



to tnat 01 



FIG . 2 83. CrabzoaeaCrWa), after the first moult. A', A" 

 first and second antennae ; A'/', A'/", the two pairs of 

 biramous appendages corresponding to the first and 

 second pairs of maxillipeds : ZS zoaea spine on the 



back (fr m ( , 1;lus) 



