1040 



CRUSTACEA. 



in rank. The largely developed mandibular palpus is not proof of 

 superiority; neither, as among the Macroura, can it be considered a 

 mark necessarily of inferiority. The species of Cyclopoidea attain 

 their largest size among the Calanidae, some in this group being a 

 fourth of an inch in length. There is also a strength and agility 

 which may perhaps be additional evidence of their superiority. We 

 commence, therefore, in our further consideration of the species of 

 Cyclopoidea, with the family Calanidae. They are pre-eminently 

 oceanic species, while the Cyclopidse are found mainly in fresh waters 

 and along sea-shores. The Corycaeidae are also oceanic species, and 

 among the Sapphirinse there are species of comparatively large size. 



The distinctive characters of many genera in these families depend 

 largely on different modes of adapting the sexes to cling together in 

 coition. These modes are as follows : — 



1. Both male antennae of the first pair with a geniculating joint, as 

 in Cyclops, Harjpacticus, &c. 



2. The right male antenna alone of the first pair with a genicu- 

 lating joint, and at the same time the right leg of the last thoracic 

 pair being large prehensile for the same purpose, as in Pontella, Can- 

 dace, &c. 



3. Neither male antenna of the first pair with a geniculating joint, 

 but both having a peculiar flexibility, which may fit them for the 

 same end, as in Setella, Clytemnestm. 



4. The male antennae of the first pair unmodified and rigid; but 

 the second pair of antennse very large and stout prehensile, as in 

 Corycceus, Sappliirina, &c. 



5. Neither pair of antennae adapted for the purpose, but the first 

 pair of feet (sometimes called outer maxillipeds), much elongated, and 

 having lateral play, as in Calanus. Calanus and Pontella pass into one 

 another by very gradual transitions. As the geniculating joint of the 

 right antenna in the Pontellae becomes weak, and the size of the poste- 

 rior thoracic legs small, this anterior pair of legs, which is rudimen- 

 tary in the more characteristic Pontellaa, as gradually enlarges and 

 takes on the Calanus form. 



6. Neither pair of antennas fitted for prehension; but both of the 

 posterior thoracic legs (a pair posterior to the four pairs of natatones, 

 and the same which on the right side is prehensile in Pontia) very 

 much elongated, nearly to the length of the body, as in Euchceta. 



These forms are illustrated in the figures already referred to, Plates 

 70 and 71, and by others on the following plates. 



