C YCLOPOIDEA. 



1031 



the non-correspondence is obvious. Other examples proving the same 

 are numerous. 



^ The position of the anterior antennae, or their angle with the medial 

 line of the body, is sometimes (as in the Calanidae) fixed and charac- 

 teristic of species. In this case they have a power of rotation at the 

 articulation with the head, by which the organ may be brought to 

 the side of the body, but no free motion back and forward. 



The setae are either naked or plumose; and some when long are 

 edged with short distant setules. They occasionally have free motion 

 at base. The setules alluded to often move freely upon the seta to 

 which they are attached. 



b. Second pair of antennce.— The antennae of the second pair are 

 very various in forms and functions. They are either simple (figs. 

 44-48), or have a lateral appendage, which though sometimes obso- 

 lescent, may be as long as the main portion (figs. 49-55).* They 

 often terminate in a few setae (fig. 44), and in some genera by a 

 long finger-like claw (figs. 46, 47). They have, therefore, at times a 

 prehensile character; and even when furnished only with terminal 

 setae, the terminal setae are generally (always ?) moveable, so as to 

 admit of being spread open or closed, in which case they act like 

 fingers in enabling the animal to adhere to surfaces. It is not 

 unusual to see a Cyclops thus resting with its posterior antennae fast- 

 ened to an object. 



Comparing these two-branched organs with others of the Cyclo- 

 poidea, but more particularly here with the natatory legs, in which 

 this structure is well exhibited, — we ascertain that the basal part of 

 these organs consists normally of two joints, the second bearing the 

 following main part of the organ, and the branch or lateral appendage. 

 In figure 51, this constitution is apparent, and we have numbered the 

 joints correspondingly, the joints of the branch being distinguished in 

 the numbering by the addition of a clash ('). There are in the figure 

 referred to, joints 1 and 2 as a base, then 3 and 4, for the main stem, 

 and 3' and 4' for the branch. A small joint may sometimes be dis- 

 tinguished on the side of joint 4, as seen in figure 54, which makes 

 the whole number of joints in the series, five. In this last-mentioned 

 figure, however, the joints 1 and 2 were not observed to be distinct. 



* Fig. 44, from a Cyclops; 45, Setella; 46, Sapphirma; 47, Corycseus; 48, Oithona; 

 49, Harpacticus; 50, Euchaeta; 51, 52, 53, Calanus; 54, Pontella; 55, Candace. 



