PELAGIC FLOATING CRUSTACEA 145 



Hyperid Amphipoda show this peculiarity — for 

 example, the relatively gigantic Cystisoma, which is 

 mesoplanktonic in deep water; and it reaches its 

 extreme in Mimonectes (Fig. 49), in which the anterior 

 part of the body is, as it were, blown out into a 



Fig. 49 — Mimonectes loveni. A Female Specimen seen from the 

 Side and from Below, showing the Distended-balloon- 

 LiKE Form of the Anterior Part of the Body. x 3. 

 (After Bovallius.) 



balloon, giving the animal the aspect of a small 

 jellyfish rather than an Amphipod. 



If, as seems probable, the body-fluid of these 

 animals is of a lower specific gravity than the sea- 

 water, it will act like the oil-globules of the Co- 

 pepoda in keeping the animals afloat. Even if the 

 specific gravity be the same, however, the distension 

 10 



