COPEPODA 10l 



male differs from the female by the presence of a fifth pair of legs which as shown in text-fig. 25 n, 

 is like that of Gaidius. 



Y (St. IV). Size of male from Thor St. 165 was 3-29 mm.; anterior division 26; nrosome 

 0-69 mm. 



The body is comparatively slender, a distinct limitation between the head and the first thoracic 

 tergite is observed, the somites IV and V are as in other stages fused with well marked lateral spines. 

 The relative length of the abdominal somites and the furca is n, 17,-19 and 13; the furcal rami 

 are 1-4 as long as wide. The antennulae extend about 3 segments beyond the end of the abdomen. 

 The maxillulae differ as usual by the 9 setae of Re, but the Easp. Ill has only 3 Sa -j- 1 Sp, and the 

 Ri I— II each 2 Sa + 1 Sp ; the laminous process of the maxillipeds has a slightly different shape with- 

 out terminal tooth (text-fig. 25 1). The pes I has Re II — III fused, but Se Re II is present; the fourth 

 pair of legs (fig. 3 g) has like the two preceding pairs, the Re II<n>III fused, with 3 Se and 16 teeth 

 in the terminal seta; the secretory pore corresponding to the Se Re II is missing. The only difference 

 between the 2 sexes is found in the presence of a fifth pair of legs of the usual rudimentary type in 

 the male (text-fig. 25 o). 



Y (St. III). Size of specimen Thor St. 167 2-48 mm. ; anterior division 2-07 mm.; urosome 0-41. 

 The shape of the body is distinctly more slender, and so is the frontal spine; the rostrum is 



blunt; the head is as in preceding stage well separated from the first thoracic somite, but also the 

 fourth from the fifth one, which has no lateral spines. The relative length between the two ab- 

 dominal somites and the furca, which is 14 as long as wide, is 12, 20 and 11. The antennulae extend 

 4 segments beyond the tip of the abdomen; the segments 2 — 3 and 4 — 5 seem to be fused, and the 

 measurements are in several respect rather different; it is curious that the segment 25, which is well 

 separated from the preceding one, is not only relatively but also absolutely longer than in any of the 

 preceding stages (it is shortest in the f °.). The maxillulae are like those of preceding stage, but differ 

 by 8 setae in the Re and by the Li I, in which one of the posterior setae is wanting (only 3 present), 

 and one of the anterior ones (S 5) is represented by a short spine. The other mouth appendages, except 

 the maxillipeds which have the the laminous process rounded, are in main features like those of 

 preceding stages (text-fig. m). 



The pes II, which like pes III — IV have the Ri unsegmented, has a fairly distinct limitation 

 between Re I and Re II — III, and is in main features like fig. 3 g; the pes III differs from II by less 

 distinct limitation between Re I and Re II e^ III, but the latter segment has only 2 Se; the pes IV 

 is again more reduced, as seen in fig. 3 h, as all the segments are completely fused, and as only a 

 single secretory pore was found. 



Variation etc. A single specimen from Thor St. 152 showed a rather curious shape of the 

 dorsal outline behind the frontal spine; as the species was in all other respects like the rest, the 

 structure ought perhaps to be regarded as a kind of deformity (text-fig. 25 f). 



"Sacshaped structures" like those described in G. tenuispinus are found in several specimens, 

 mostly adult females, but also in young ones of the penultimate stage; the following number of "para- 

 sites" were found in samples from the following 6 stations of Thor viz. J 9/ 6 1904 St. 152 7 parasites in 



