PARASITIC COPEPODS—CALIGIDM— WILSON. 



541 



the aquarium. At the same time the first antenna? begin to show signs 

 of segmenting into two joints, and upon the ventral surface of the 

 posterior part of the body numerous fine lines appear curving- from 

 the outer edge inward and backward toward the anus (fig. 39). 



These represent the seta? of the new appendages which are to appear 

 with the second moult. This 

 moult occurs during the sec- 

 ond thirty-six hours and the 

 larva comes forth radically 

 changed in man}' particulars. 

 The body has elongated more 

 than 50 per cent, while it has 

 broadened scarcely half that 

 amount, with the result that 

 it appears much narrower 

 than before (fig. 40). The 

 pigment now covers a wider 

 space along the margin and is 

 more uniformly distributed. 

 The median nauplius eye has 

 disappeared and instead we 

 find the pair of simple eyes 

 fused on the median line 

 which are to characterize the 

 adult. They are situated 

 farther back in the carapace 

 and in front of them a large 

 mass of pigment extends the 

 entire width of the carapace. 

 This latter is much more 

 clearly defined and now cov- 

 ers about two-thirds of the 

 entire body. There are two 

 free thoracic segments, each 

 bearing the rudiments of a 

 pair of swimming legs, and 

 each more or less fused with 



the head. 



They arc followed by a 

 third segment, and this in 

 turn by an abdomen. The 



latter is short and terminated by a pair of blunt anal lamina? (fig. 41). 

 Each Lamina carries on its inner margin a stout two-jointed seta. The 

 shorter basal joint has a row of delicate, hairs upon its inner margin, 

 while the longer distal joint is plumose. Opposite this seta on the 

 end of the lamina there is a long slender spine, and on the outer margin 

 are three shorter curved spines. 

 Proc. X. M. vol. xxviii— (i4 35 



Fig. 10.— The metanauplius of Caligus bonito, dorsal 

 view. Pigment uneven and a rusty-brown color. 



