no. 1404. PARASITIC COPEPODS—CALIGIDJE— WILSON. J)23 



second maxillae, and the eighth (8) the muscles of the lateral area of 

 the carapace. 



The ninth nerves (9) arise from the anterior lateral margin as a 

 single pair, each of which soon subdivides into four branches which go 

 to the first maxillipeds and adjacent muscles. 



The tenth pair (10) have their origin in the posterior part of the 

 lateral margin and, subdividing into three branches, pass to the second 

 maxillipeds. These nerves are very large and indicate again the 

 importance of the appendages to which they go as prehensile organs. 



At the posterior end of this ventral ganglion are given off the 

 eleventh, twelfth, and thirteenth pairs. The eleventh pair (11), which 

 are on the outside, go to the first legs and adjacent muscles. The 

 twelfth or middle pair (12) innervate the second legs and the muscles 

 of the thoracic area of the carapace. The thirteenth or inner pair (13) 

 art' so close together as to be distinguished with some difficulty. They 

 extend backward side by side along the mid line of the body, through 

 the free segment and into the genital segment, where they separate 

 considerably, passing into the abdomen at about the centers of the 

 right and left halves. Each nerve gives off a branch to the third and 

 fourth swimming leg on its side, a large branch in the genital segment, 

 which courses along the lateral margin and terminates in the fifth leg, 

 and on entering the abdomen divides into two branches, one passing 

 to the anus and the other to the anal lamina. 



In OaMgus the structure and arrangement of the ganglia and their 

 nerves is almost identical with that in Lepeophtheirus, but the distri- 

 bution as given by Pickering and Dana for C. curtus differs in several 

 particulars. 



Of the three pairs given off by the superior ganglion the first is the 

 same but the second goes to the frontal plates, while the third goes to 

 the terminal joints of the first antenna 1 . On the inferior ganglion an 

 extra pair arise close beside the fourth pair, which innervate the pro- 

 boscis. The fifth pair go to the second antenna 1 instead of the frontal 

 plates. All the other pairs are identical, save that the sixth, seventh, 

 and eighth pairs are united at their roots and appear as branches of a 

 single nerve rather than three separate pairs. There is also an extra 

 pair close to the tenth which help to innervate the second maxillipeds. 

 Thus, out of thirteen pairs ten are identical in the two genera, while 

 thf other three innervate the same regions but are interchanged, the 

 nerve entering the frontal plates being first in Caligus and last in 

 I .< i'i ophthi irws. 



It must be remembered that Pickering and Dana mistook the nature 

 of several of the appendages, notably the antenna 1 . They understood 

 that the lirst antennae, or their rudiments, were situated in the central 

 incision of the frontal plates, while the actual lirst antenna 1 they con- 

 sidered as the second, and they called the second antennae the first 



