330 EARTH TRESPASSERS. 



perch is able to sustain life while out of the water by 

 an apparatus which keeps the gills moist, and enables 

 them to perform their functions. A similar provision 

 is to be found in the crabs and lobsters, although it is 

 carried out in a different manner, which can be under- 

 stood by any one who will take the trouble of opening 

 a lobster. 



When the shell of the " head," as it is called, is 

 removed, there are seen on either side a number of 

 whitish pointed objects, which go by the popular name 

 of "lady's fingers," and are rejected as uneatable. 

 If one of these fingers be removed and bent, it will be 

 seen to consist of a vast number of delicate plates set 

 very closely side by side. These are the gills or 

 respiratory apparatus of the lobster; and, as long as 

 they are kept moist, the creature can live. 



Being protected as they are by that portion of the 

 shell which encloses them, and is technically known 

 as the carapace, there is but little evaporation ; while 

 their great comparative volume enables them to retain 

 a considerable amount of water. Should they become 

 at all dry, their moisture "may be renewed by a short 

 dip in the water, and the animal has another lease of 

 life. 



Not all the Crustacea can thus endure a long 

 absence from the water ; but there are several species 

 which can survive without water for many days ; and 

 there are some which live almost entirely on land, and 

 only pay occasional visits to the water. 



One of this species, the Robber Crab (Birgus latro), 

 presents a curiously exact parallel to the climbing 

 perch : not only being able to live for a considerable 



