CRUSTACEA. 



393 



FIG. 218. MASTIGOPUS STAGE 

 OF SEKGESTES. (From Glaus.) 

 Mf". maxilliped 3. 



The most obvious external 

 indications of the passage from 

 the Acaiithosoma to the Mas- 

 tigopus stage (fig. 218) are to 

 be found in the elongation of 

 the abdomen, the reduction 



and flattening of the cephalo-thoracic shield, and the 

 nearly complete obliteration of all the spines but the 

 anterior. The eyes on their elongated stalks are still 

 very characteristic, and the elongation of the flagellum 

 of the second pair of antennae is very striking. 



The maxillae and maxillipeds undergo consider- 

 able metamorphosis, the abdominal feet attain their 

 adult form, and the three anterior thoracic ambu- 

 latory legs lose their outer rami. The most re- 

 markable change of all concerns the two last pairs 

 of thoracic appendages, which, instead of being me- 

 tamorphosed like the preceding ones, are completely or nearly com- 

 pletely thrown off in the moult which inaugurates the Mastigopus 

 stage, and are subsequently redeveloped. With the reappearance of these 

 appendages, and the changes in the other appendages already indicated, the 

 adult form is practically attained. 



With reference to the development of the majority of the 

 Carabidae, Penaeinte, Palnemoninae, Crangoninse, it may be stated 



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