404 CRUSTACEA ENTOMOSTRACA. 



sometimes by the mandibles as well, which reappear and grow 

 out into long tentacular appendages, comparable in their 

 function with the root-like appendages of the Cirripede Rhizo- 

 cephala. Having attained the adult stage the animals throw off 

 these appendages, and leave the body of the host to assume 

 their brief pelagic existence, which comes to an end after the 

 maturation and discharge of the sexual products. 



Sub-order 1. EUCOPEPODA. 



Copepoda ivith masticatory or suctorial mouth parts, and sivim- 

 ming feet the branches of which are two- or three-jointed. 



The seventeen families into which the Eucopepoda have been 

 divided are arranged (following Gerstaecker) in six series. 

 The first consists of free-swimming forms ; the fourth, fifth 

 and sixth of parasitic forms. In the second and third series 

 while some members are free-living, others are adapted to a 

 commensal or semiparasitic mode of life. A much larger 

 number of families is recognized by more recent writers, but 

 no complete classification of the sub-order is at present 

 available. 



The first two families, the Pontellidae and Calanidae, are included 

 by Giesbrecht in his group Gymnoplea, which is characterized by the fol- 

 lowing features. They are free and powerfully swimming pelagic Copepods 

 with long and many-jointed (24-25) anterior antennae, and biramous pos- 

 terior antennae. 5th and 6th thoracic segments closely united and separ- 

 ate from the urosome, and in the male the appendage of the 6th modi- 

 fied, often unsymmetrically, as copulatory organs ; urosome, 5-jointed 

 in male ; male organs unsymmetrical ; heart usually present : the eggs 

 are laid separately or carried by the female in a single egg-sack until 

 they are hatched. 



First series (Fams. 1-4). 



Fam. 1. Calanidae. (Amphaskandria of Giesbrecht). The anterior 

 antennae of the male are nearly or quite symmetrical, and more abun- 

 dantly beset with sensory organs than in the female. In the female the 

 5th pair of swimming feet may be reduced or entirely absent, and the 

 4th and 5th segments are generally fused. 



Calanus Leach, C. finmarchicus Gunner (17l>-~>). abundant in X. Atlantic 

 (Fig. 260). Eucalanus Dana, Rhincalanus Dana. MecynoceraThomp., Para- 

 calanus Boeck, Acrocalanus Giesb., Calocalanus Giesb., C. pavo Dana ; in the 

 female (iv. 15)* the anterior antennae bear long bristles, of which three 



* These numbers refer to the plates and figures in Giesbrecht's Mono- 

 graph on Pelagic Copepods, Fauna and Flora <>f tin- (inlf of Xaples, vol. 19. 



