MARINE BIOLOGICAL STATION AT POUT ERIN. 



91 



The Isopods, unlike the Amphipods, have for the 

 most part broader and flatter bodies (fig. XIV.), are 

 depressed from above downwards, have the legs shorter 

 and less conspicuous, and run or creep in place of leaping. 

 The tail legs which were used for leaping in the Amphi- 

 pods are in part breathing organs in the Isopods, and these 

 parts are enclosed within flap-like folding doors. Many of 

 the Isopods, although true water-breathers, can live the 



/ Idothea baltica. 2. Astacilla longicornis 3. Ligia oceanica. 

 1 3 



Fig. XIV 



greater part of their time on land. Idothea haltica, shown 

 at 1 (fig. XIV.), is completely aquatic, and lives on green 

 and brown sea-weeds, which it generally resembles closelv 

 in colour ; while Ligia oceanica (No. 3) is found at or even 

 above high tide mark, generally hiding in crevices of the 

 rock or between the stones of a pier during the day and 

 coming out to run about and feed at night. Astacilla 

 longicornis (2) is of a white colour, and can only be 



