AMPHIPODA. 



277 



Order AMPHIPODA. 



The Amphipods are allied to the Isopods, but the majority are recognisable 

 by having the body narrow and flattened from side to side, instead of broad and 

 flattened below. Moreover, the gills are attached to the thoracic feet, and the 

 latter, instead of being 

 broad, leaf -like, and 

 overlapping, are foot- 

 like, elongate, and used 

 for leaping or swim- 

 ming. 



In the suborder 

 Gammaridea the eyes 

 are mostly of small 

 size, and seldom pro- 

 minent. The head 

 does not coalesce with 

 the first segment of 

 the thorax, and the 



maxillipedes have a distinct palp ; the abdomen being well developed, and 

 bearing appendages. The form of the body is shown in the illustration of the 



fresh- water shrimp (Gammarus pulex), and the sand- 

 hopper (Talitrus locusta). The latter lives near the 

 edge of the sea, beneath seaweed, or other substances, 

 which prevent the evaporation of the moisture from 

 the sand. Sand-hoppers usually progress on land by 

 leaps; and although some nearly allied forms are 

 found far from the sea, the majority of the Gam- 

 maridea are marine, swimming by means of the con- 

 stant play of their abdominal appendages, and, when 

 thrown on the land, wriggling helplessly along on their 



FRESH-WATER SHRIMP (enlarged). 



SAND-HOPPER (enlarged). 



sides. The fresh- water shrimp 

 is common in the streams and 

 ditches of Europe. During 

 the cold months of the year 

 they bury themselves in the 

 mud, but emerge from their 

 winter-quarters on the first 

 warm days of spring. 

 Amongst deep-water forms, 

 perhaps the most noteworthy 

 are AcantliecJiinus tricari- 

 natus,andAndania gigantea. 

 The former has developed a 

 spiny process at almost every 

 possible point, each of the 



SPINY SHRIMP, Acanthechinus tricarinatus (nat. size). 



