580 PROCEEDiyOS OF THE NATIONAL MUSEUM. vol.47. 



The jirst maxillae {mx, fig. 3) are very rudimentary and palplike 

 and contain no cliitin, but are soft and flexible like the first antennae. 

 They have been variously interpreted by different authors, the most 

 of whom have called them palps and have connected them with the 

 second antennae or the mandibles. But Kurz proved conclusively 

 that they are appendages of the same rank as the antennae and man- 

 dibles; that they have no connection with either, but are moved by 

 an entirely independent set of muscles, and that in the majority of 

 instances they are themselves furnished with a A^ery respectable 

 palp. Furthermore, it was found by the present author ^ that these 

 appendages are innervated by a separate nerve from the infra-esopha- 

 geal ganglion, which adds the final touch to the proofs already accu- 

 mulated. Their position is on the sides of the proboscis, close to its 

 base and much nearer the ventral than the dorsal margin, and they 

 do not usually reach beyond the mouth opening. Their general form 

 is narrow and cylindrical, slightly contracted at the base where they 

 join the proboscis, and divided at the tip into two or three fingerUke 

 rami, each of which terminates in a stout and acuminate soft seta. 

 At or near the center, on the ventral surface and at the inner margin, 

 each maxilla gives off a palp, which is usually divided at the end, 

 like the maxiUa itself, into two or three fingerlike processes, each 

 armed with a soft seta. There is no genus in which the maxillae show 

 definite segmentation, but they always appear one-jointed. 



The maxillae in the male correspond very closely with those of the 

 female of the same species. 



The second maxillae have become the principal organs of attach- 

 ment in the present family, and accordingly we find them modified 

 in various ways to serve this function. When they first appear in 

 the metanaupHus stage they are clawed appendages, similar in all 

 respects to the maxilhpeds. In the free-swimming or first cope- 

 podid stage, when the larva attaches itself to its host or shortly 

 afterwards, these second maxillae are fastened to the proximal end of 

 the frontal filament. In the female this union of maxillae and 

 filament becomes permanent throughout life, and the two fuse 

 thoroughly until all that is left of the filament is the button or bulla 

 which joins the tips of the maxillae and serves to anchor them firmly 

 in the tissue of the host. No such union takes place in the male and 

 his second maxillae remain clawed appendages, very similar to the 

 maxiUipeds. 



In the female, after the fusion of the maxiUae and filament, the 

 former lose theh claws and all traces of segmentation. Even the 

 internal muscles are entirely changed and become longitudinal 

 bundles running the whole length of the appendage without a break. 

 This length varies greatly in the different genera and furnishes, with 



> Proc. U. S. Nat. Mus., vol. 39, pi. 34, fig. 33. 



