PARASITIC COPEPODA. 197 



Colour of preserved material a uniform yellowish white without pigment spots or 

 lines. 



Male, Carapace ovate and narrowed anteriorly, with grooves and markings on the 

 dorsal surface like those of the female, but it is relatively larger, being more than 

 half the entire length, and nearly as wide as long. The eyes are distinct and small, 

 about one-third the distance from the anterior margin. 



The second and third thorax segments are wider than in the female ; the fourth 

 segment is the same width as the genital segment and only a trifle longer than the 

 second and third segments. The genital segment is elliptical-oblong, one-fourth 

 longer than wide, and not quite one-fifth of the entire length. Both the fifth and 

 the sixth legs are visible dorsally, the former on the lateral margins at about the 

 centre of the segment, the latter at the posterior corners. 



The abdomen is two-jointed and at least one-half shorter than the genital segment ; 

 the two joints are equal in size. The anal laminae are narrow, but nearly as long as 

 the entire abdomen, each tipped with four very long plumose setae. 



Appendages and colour as in the female. 



Total length 275 millims., length of carapace (including third thorax segment) 

 1*4 millims., width of same 1*3 millims., length of genital segment 0*5 millim., 

 length of abdomen (including anal laminae) 0*6 millim. 



Developmental stages. Young females were obtained in two stages of development 

 respectively 2*5 millims. and 3*5 millims. long. 



In the former, the second thorax segment is not yet fused with the carapace, but 

 is semilunar in shape, with the convex side projecting a little way into the posterior 

 portion of the carapace. The lateral processes on this segment are nearly as large as 

 the posterior lobes of the carapace (fig. 32). 



The third segment is much narrower than the second, but is still wider than it is 

 long. The fourth segment is considerably longer than wide and has a broad spindle 

 shape. In the genital segment each of the posterior angles projects strongly sidewise, 

 is well rounded, and armed with two stout spines. This makes the segment twice as 

 wide across the posterior margin as across the anterior. The abdomen is also slightly 

 wider at its posterior end. 



The first antennae are short and thick and are appressed closely to the margin of 

 the carapace. The other appendages are similar to those of the adult except the 

 swimming legs, in which the rami have but two joints instead of three. 



In the later developmental stage the carapace has enlarged considerably, and the 

 second thorax segment has widened with it (fig. 33). The longitudinal and trans- 

 verse grooves on the dorsal surface of the carapace are now fully formed, so that the 

 same areas are seen as in the adult. The third and fourth thorax segments are 

 about the same as in the previous stage, but the genital segment has changed 

 radically. It has widened into a broad acorn shape, as wide anteriorly as posteriorly, 

 with the posterior comers projecting slightly backwards and showing the fifth 



