INTRODUCTION. 1 1 



host to enable either the mouth-organs or swimming 

 feet to have free play. The sternal fork, however, is 

 not articulated, neither is it flexible.* 



The external openings are the mouth, the vulvas and 

 apertures of the oviducts in the female, the vasa 

 deferentia in the male, and the anus. The mouth is 

 situated on the ventral surface of the cephalo-thorax, 

 and is placed at the apex of a short, conical, movable 

 tube. The vulvas are situated on each side of the 

 middle line at the posterior end of the genital seg- 

 ment and communicate with the receptacula seminis. 

 They are difficult to see in the adult female, but each 

 has frequently a spermatophore attached which indi- 

 cates the position. The openings of the oviducts are 

 in the same segment, but nearer the lateral margins 

 and just under the fifth feet. The openings of the 

 vasa deferentia are situated on the postero-lateral 

 margins of the genital segment of the male. The anus 

 is in the middle line at the apex of the abdomen. In 

 addition to these more important openings, there are 

 also apertures of pore-canals and glands on the 

 anterior surface of the basal joint of the protopodites 

 of the second and third pairs of feet, and also on the 

 dorsal surface of the cephalo-thorax and abdomen. 

 The opening in some cases is at the apex of a small 

 papilla, and communicates with a sac in the interior. 

 The function of these glands is uncertain, but it is 

 possible that it is connected with the aeration of the 

 blood. If a little methylene blue solution be added 

 to the sea- water in which the parasites are living, a 

 general staining takes place, but the glands are more 

 deeply stained than the rest of the body. 



* Fig. 1, PI. XIII, shows the general arrangement of the appendages in 

 Lepeophtheirus. 



