370 



ARTHROPODA 



segmentation is visible, while the appendages are rudimentary or even entirely 

 lost. Indeed one would not recognize them as arthropods save for the following 

 features: 



(i) Most of them have the typical Copepod egg-sacs attached to the hinder 

 end. (2) A complete series of intermediate forms allows one to trace, step by 

 step, the alterations of form from the free-living species to the most modified 

 parasites. (3) Ontogeny is convincing. Most parasitic Copepoda leave the 

 egg as a nauplius and pass through a Cyclops-stage before attaching themselves 



a. 



FIG. 386. FIG. 387. FIG. 388. 



FIG. 386. Female Lernccocera esocina (from Lang, after Claus). A, armlike 

 processes of anterior end; d, digestive tract; es, egg-sacs; od, oviduct; / r / 4 , rudimentary 

 thoracic appendages. 



FlG. 387. Argulus foliaceus (from Ludwig-Leunis). a, sting; a', antenna; b, 

 mouth; c, intestine with liver; d, abdomen; pm 1 , pnr, first and second maxillipeds; 

 p l -p*, biramous feet of thorax. 



FIG. 388. Lerncea branchialis* (orig.). 



to fishes and becoming the highly degenerate parasites. These parasites are 

 always females. The males scarcely pass the Cyclops-stage, copulate with the 

 females and then die, or if they pass through the metamorphosis, they remain 

 small and different in appearance (fig. 8). They occur attached to the female 

 near the genital openings. There is thus here a marked sexual dimorphism. 



ARGULID^; (sometimes made a distinct order, Branchiura), fresh- water forms 

 with compound eyes, liver lobes, and second maxillipeds metamorphosed into 

 suckers. A r gains* (fig. 387). CALIGID.E (C aligns*), marine and brackish- 

 water. LERN^OPODID^E. Fish parasites with maxillae united into an adhesive 

 organ. Achthercs* (fig. 6), perch. LERN^HXE; worm-like parasites. Lerna'a* (fig. 

 388) ; Lenieeocera* (fig. 386) ; Pcnclla* 



