364 



The period of reproduction of P. pacifica is quite protracted. Accord- 

 ing to Bowman (1960), during the course of their life the crustaceans 

 reproduce at least twice and, possibly, oftener. The number of eggs in the 

 brood pouch varies from 20 to 60, whereas in the much larger P. japonica 

 may be as high as 200. 



4. Parathemisto (Euthemisto) libellula (Lichtenstein, 1822) (Figs. 153, 

 154) 



Lichtenstein, 1822: 32 (Gammarus); Goes, 1866: 533 (Themisto); 

 bovallius, 1889: 281 (Euthemisto); Sars, 1893: 13; Stephensen, 1923: 

 24 (Themisto); Schellenberg, 1927: 627; Vinogradov, 1956: 211 

 (Euthemisto); Barnard, 1959: 123; Bowman, 1960: 382. 



This is a much larger species of the genus. Sexually mature speci- 

 mens are generally up to 30 mm in length but females sometimes up to 

 60 mm. 



The somites of the pereon and pleon are without dorsal denticles. The 

 head is spherical and the lower frontal angle round. Antennae I and II in 

 females are approximately equal in length; the flagellum of antennae I 

 is conical and the thin distal part not curved. In young males anten- 

 nae I are almost the same in structure as in females and their flagellum 

 unsegmented. Antennae II in females and young males are somewhat 



297 



Fig. 153. Parathemisto (Euthemisto) libellula (Linchtenstein), female (after Sars, 1890). 



