CRUSTACEA. 



407 



its host. Underneath the Nauplius skin a number of appendages are 

 visible, which become functional after the first ecdysis. This takes place 

 within a few hours after the hatching of the Nauplius, and the larva then 



at i 



FIG. 230. SUCCESSIVE STAGES IN THE DEVELOPMENT OF ACHTHEBES PEBCARDM. 

 (Copied from Bronn ; after Glaus. ) 



A. Modified Nauplius stage. B. Cyclops stage. C. Late stage of male embryo. 

 D. Sexually mature female. E. Sexually mature male. 



at 1 , first pair of antennas ; at 2 , second pair of antennas; md. mandible; m.r. maxillae ; 

 pm l . outer pair of masillipeds; pm' 2 . inner pair of maxillipeds; p l . first pair of legs; 

 p' 2 . second pair of legs; z. frontal organ; i. intestine; o. larval eye; b. glandular body; 

 t. organ of touch; ov. ovary; /. rod projecting from coalesced maxillipeds; </. cement 

 gland; rs. receptaculum seminis; n. nervous system; te. testis; v. vas defereus. 



passes from this rudimentary Nauplius stage into a stage corresponding 

 with the Cyclops stage of the free forms (tig. 230 B). In the Cyclops 

 stage the larva has an elongated body with a large cephalo-thoracic shield, 

 and four free posterior segments, the last of which bears a forked tail. 



There are now present eight pairs of appendages, viz. antennae (two pairs), 

 mandibles, maxillae, maxillipeds, and three pairs of swimming feet. The 

 Nauplius appendages are greatly modified. The fii-st pair of antennae is 

 three-jointed, and the second biramous. The outer rarnus is the longest, and 

 bears a claw-like bristle as its extremity. This pair of appendages is used 

 by the larva for fixing itself. The mandibles are small and connected 

 with the proboscidiform mouth ; and the single pair of maxilla? is small 

 and palped. The maxillipeds (pnt 1 and pm?} are believed by Claus to be 

 primitively a single birarnous appendage, but early appear as two distinct 

 structures', the outer and larger of which becomes the main organ by 

 which the larva is fixed. Both are at this stage simple two-jointed 



1 Van Beneden (No. 506) in the genera investigated by him finds that the two 

 maxillipeds are really distinct pairs of appendages. 



