84 HISTOKY OF CRUSTACEA. Chap. IX. 



Nauplius- and Zoea-stages, which in the Decapoda occur 

 ]3artly (in Feneus) in the free state." "Therefore," 

 says he, " I regard Nebalia as a Phyllopodiform Deca- 

 pod." The youngest larvae [of the Phyllopoda] are 

 Nauplii, which we have ah-eady met with exceptionally 

 in some Prawns, and which we shall now find repro- 

 duced almost without exception. The body-segments 

 and feet, which are sometimes so numerous, are formed 

 gradually from before backwards, without the indication 

 of any sharply-discriminated regions of the body either 

 by the time of their appearance or by their form. All 

 the feet are essentially constructed in the same manner 

 and resemble the maxillae of the higher Crustacea.^ 

 We might regard the Phyllopoda as Zoeae which have 

 not arrived at the formation of a peculiarly endowed 

 abdomen or thorax, and instead of these have repeatedly 

 reproduced the appendages which first follow the 

 Nauplius-limbs. 



Of the Copepoda — some of which, living in a free 

 state, people the fresh waters, and in far more multi- 

 farious forms the sea, whilst others, as parasites, infest 

 animals of the most various classes and often become 

 wonderfully deformed — the developmental history, like 

 their entire natural history, was, until lately, in a very 

 unsatisfactory state. It is true, that we long ago knew 

 that the Cyclopes of our fresh waters were excluded in 

 the Nauplius-form, and that we were acquainted with 

 some others of their young states; we had learnt, 



2 "The maxilla of the Decapod-larva (Krebslarve) is a sort of 

 Phyllopodal foot" (Claus). 



