CRUSTACEA COPEPODA 



CHAP. 



the mouth and its appendages, dividing the free-living and 

 semi-parasitic forms as Gnathostomata from the true parasites or 



FIG. 25. Calanus hyperboreus, x 30. Abd 1 , First abdominal segment ; 1st Ant, 

 2nd Ant, 1st and 2nd antennae ; Md, mandible ; Mx l , My?, 1st and 2nd maxillae ; 

 Mxp, maxillipede ; Tfi 1 , 1st thoracic appendage. (After Giesbreclit. ) 



Siphonostomata. This division, although convenient, breaks 

 down in many places, and it is clear that the parasitic mode of 

 life has been acquired more than once in the history of Copepod 



