542 



PROCEEDINGS OF THE NATIONAL MUSEUM. 



VOL. XXVIII. 



Fig. 41.— Anal laminae of the meta 

 nauplius of caligus bonito. 



This alters the appearance of the larva completely, but the greatest 

 change has taken place in the appendages. The locomotor organs of 

 the nauplius have entirely disappeared, and in their place stand append- 

 ages which are evidently the rudimentary 

 forms of those found in the adult. 



The first antennae are now distinctly two- 

 jointed, the basal joint carrying a single 

 seta at about the center of its anterior 

 margin, while the terminal joint is tipped 

 with from seven to nine short plumose 

 setae irregularly arranged (fig. 40). Fur- 

 thermore, instead of projecting directly 

 forward in front of the body, as they did 

 in the nauplius, these appendages are now 

 appressed close to the anterior margin of 

 the carapace. Their basal joints lie in 

 exactly the position afterwards occupied 

 by the frontal plates, and are already 

 partially fused with the carapace. The 

 terminal joints, which are somewhat elongated, project at right angles 

 to the body axis in the same position which they occupy in the adult. 

 The second antennae have changed even more. They still retain 

 their biramous character, but have become prehensile organs instead of 

 locomotor (fig. 42). Each consists of a long and very stout basipod 

 from which project the shorter terminal segments. 



The latter are fused for a distance and then separate at nearly right 

 angles. The exopod is consid- 

 erably the shorter of the two 

 and is terminated by a short 

 rudimentary spine. 



The endopod is much stouter 

 and terminates in a single 

 curved claw, nearly as long as 

 the endopod itself, and bent 

 over ventrally until its tip 

 points in toward, and nearly 

 touches, the ventral surface of 

 the basipod. These are mani- 

 festly intended for clasping or- 

 gans and in furtherance of that 

 design they extend forward in 

 nearly the same position as that 

 occupied by the first antennae of the nauplius. Moreover, the larva 

 keeps snapping them viciousby, giving a forward and downward rake 

 in the evident endeavor to hook them into something. They must be 



Fig. 42. — The second antennae of the metanau. 

 plius of Caligus bonito. 



