VIII 



ARTHROPODA 



21*7 



are developed. This larva is shown to belong to a Stomatopod by 

 the fact that it possesses already two stalked compound eyes, which 

 distinguish it from the Metanauplii of all other groups of Crustacea. 

 It has a triangular carapace resembling that of the Zoaea larva, and 

 the hinder part of the body is formed of an unsegmented abdomen 

 terminating in a jointed caudal fork. 



The next stage in the life-history which is known is the Erich- 

 thoidina stage, which Balfour compared to a Zoaea larva. In this stage 

 the larva has a precisely similar carapace and stalked eyes, but the 

 first antenna has developed a second flagellum and so become forked, 

 whilst the second antenna is now unforked. There are the usual 

 three pairs of jaws, and these are followed by no less than five pairs 



mxp~ 



FIG. 165. Two stages in the development of a Stomatopod larva. 

 A. After Lister. B. After Hansen (from Lister). 



A, Early " Metananplius " stage. B, So-called " Zoaea " or Erichthoidina stage, d.sp, dorsal spine ; 

 <7./..s-y. 'lorso-lateral spines ; mxp 1 ' 5 , the five maxillipedes ; pi, the rudiment of the appendage of the lirst 

 segment of the abdomen. 



of forked swimming appendages. The abdomen is, however, almost 

 unsegmented, only the first segment with rudiments of its appendages 

 being present, and it ends like the abdomen of most Zoaeae in a broad 

 tail-fan. Thus the larva is more like a Mysis larva than a Zoaea, but 

 differs from both these types of larvae in the character of the abdomen. 

 In subsequent moults the abdomen becomes segmented and 

 develops its appendages, whilst the endopodite of the second appendage 

 of the thorax develops into a great hooked claw, and the first 

 appendage develops into a long slender unforked limb, the hinder 

 three pairs of appendages dwindle into insignificant rudiments or 

 vanish altogether. In this way the Erichthus stage is reached, which 

 is sometimes termed a Pseudozoaea because it has only the first 

 two pairs of thoracic appendages well developed, the next three being 

 represented by mere stumps, and the appendages of the hindermost 

 thoracic appendages being totally absent. This is transformed into 



