19 



ON THE CRUSTACEA. 



By ALEXANDER MEEK. 



1.— Larval Nomenclature 19 



2.— Growth 23 



1.— LARVAL NOMENCLATURE. 



The nomenclature of the larvae of Crustacea has got into a 

 state of considerable confusion. At all events, no one appears 

 to be able to say definitely what is meant by the terms Protozoea 

 and Zoea. Even with reference to the Decapoda these names 

 are indifferently applied to very different larvae and stages ; 

 protozoeae may have seven, eight or thirteen appendages, and 

 zoese seven, eight, twelve or thirteen pairs. 



There is fortunately no trouble as to the nauplius. Whatever 

 its shape, it is a larva with the three anterior pairs of appendages ; 

 and we apply the convenient term metanauplius to the imme- 

 diately succeeding stages in which segmentation takes place, 

 and the next few pairs of limbs make their appearance. We 

 can refer therefore with precision to larvae which are hatched 

 at the nauplius or at the metanauplius stage and to the meta- 

 nauplius phases of the former. 



At whatever stage the larva is liberated from the egg, whether 

 at the nauplius or at some later phase, a series of ecdyses are passed 

 through during which the remaining limbs are developed and 

 grow. The limbs may all remain in a rudimentary condition until 

 the number has been completed, or they may advance into a 

 functional state in groups. My suggestion is that we can best 

 define the stage at hatching and the subsequent stages by refer- 

 ence to the appendages which have been fully developed. To 

 give point to my plea, I have prepared a chart (fig. 1) which 

 indicates the nature of the development with reference to the 

 appendages in the various groups. The nineteen appendages of 



