TYPE CRUSTACEA. 



407 



Branchiae are present in Mysis only in the form of small 

 epipodial elevations of the thoracic appendages, and in Siriella 

 as coiled tubular structures on the protopodites of the abdom- 

 inal appendages of the males. In Euphausia, however, they 

 form large ramified bunches attached to the protopodites of 

 the thoracic limbs and are present even on the rudiments of 

 the seventh and eighth pairs ; they are not, however, enclosed 



ot 



FIG. 184. Mysis relicta (after SARS). 

 bp brood-pouch. ot = otocyst. 



within a chamber formed by the lateral portions of the cara- 

 pace, but project freely to the exterior. 



Otocysts occur in the inner lamellae of the sixth abdominal 

 appendages (Fig. 184, ot), and in Euphausia a number of eye- 

 like phosphorescent organs occur on the basal joints of the 

 second and seventh thoracic appendages as well as upon the 

 ventral surface of the four anterior abdominal segments. 

 They are spherical in shape and each consists of a cup of 

 cells containing red pigment covered in by a lens. 



The Schizopoda are essentially marine, though some 

 species of the genus Mysis (Fig. 184) occur in fresh and 

 brackish water. 



2. Order Cumacea. 



In this order the carapace covers only the anterior three 

 or four thoracic segments, five or four of them remaining dis- 

 tinct. The antennules are short and in the male biramous, 

 while the antennae, though in the female almost rudimentary, 

 may be as long as the entire body. The two anterior thoracic 

 appendages form maxillipeds, their basal joints serving for 

 mastication while the succeeding six pairs are limblike, all 

 but the last or three last possessing small exopodites. The 



