PARASITIC COPEPODA. 207 



of demarkation except the position of the fourth legs on the ventral surface. This 

 fused portion constitutes the body of the Copepod, which is nearly twice the width of 

 the head, and twice as long as wide, with parallel sides. 



The body widens sharply from the neck, its anterior corners well rounded, while its 

 posterior corners are produced into a pair of wide, flattened processes, nearly as long 

 as the rest of the animal, and either straight or slightly divergent, Along the sides, 

 toward the centre, these processes often show incisions arid grooves, very irregularly 

 placed in different specimens and suggesting imperfect segmentation. 



Between the bases of these processes lies the small abdomen, a little wider than 

 the processes, and also a little wider than long. Its posterior corners are produced 

 into short and rounded processes, similar to those on the genital segment but much 

 smaller. Between these processes on the posterior margin are the tiny anal papillae, 

 each of which terminates in three non-plumose setse. Of these latter, the inner and 

 outer ones are considerably longer than the middle one (fig. 66). 



The first antennae are reduced to mere knobs, so rudimentary as to be invisible 

 unless seen in profile and under the best conditions. The second pair are much 

 enlarged and extend forward diagonally in front of the head. They are the organs 

 of prehension and consist of an enlarged basal joint filled with strong muscles, and a 

 stout terminal claw which is buried in the flesh of the host. The basal joints are 

 united throughout their entire length, and are enlarged at the end into a double 

 disc, from the edge of which on either side project the terminal claws. The mouth- 

 tube is a simple hollow cone projecting but little from the ventral surface ; the 

 mouth-parts have all been aborted, with the exception of the second maxillipeds. 

 These* appear as tiny two-jointed appendages on either side of the base of the 

 mouth-tube (fig. 64). 



There are four pairs of rudimentary legs, the first three of which are close together 

 on the thorax segments which form the neck, while the fourth pair are some distance 

 farther back on the ventral surface. We may presume that the line of junction of 

 the fourth and genital segments is just behind the bases of these legs. Each leg 

 consists of a triangular basal lamina tipped with two minute, one-jointed rami 

 scarcely larger than spines, and naked. 



Colour a dark grey by reflected light, a greyish yellow by transmitted light. 

 Under the latter conditions spots of dark pigment are seen along the sides of the 

 head and neck, at the posterior end of the genital segment, and along the centre of 

 the posterior processes. The two oviducts also show through the dorsal surface of 

 the genital segment as two broad lines of dark brown, broken up into separate 

 spherical eggs. 



Total length 2'35 millims., length of head 0'35 millim., length of genital segment 

 079 millim., length of posterior processes 1 millim., length of egg-strings 0'6 millim., 

 width of genital segment 0'4 millim. 



. Similar to the female, but with certain marked differences in the body 



