102 ANIMAL FORMS 
millions are caught each year, and to such an extent has 
their destruction proceeded that in many places they are 
well-nigh exterminated. At the present time, however, leg- 
islation, numerous hatcheries, and a careful study of their 
life habits is doing much to better matters and inciden- 
tally to put us in possession of many interesting zoological 
facts along this line, some of which will be mentioned later. 
Frequently the prawns, especially the larger ones, and a 
spiny lobster (Palinurus), are mistaken for crayfishes or 
lobsters, but they differ from them in the absence of the 
large grasping claws. 
Along almost any coast some of these animals are to be 
found, often beautifully colored and harmonizing with the 
seaweeds among which they live, or so transparent that 
their internal organization may be distinctly seen. Farther 
out at sea other species swim in incredible numbers, feed- 
ing upon minute organisms, and in turn fed upon by numer- 
ous fishes and whales; and, especially on the Pacific coast, 
shrimp-fishing is an important industry. 
103. The hermit-crabs——The last of these long-tailed 
decapods is the interesting group of the hermit-crabs, 
which occur in various situations in the sea. In early life 
they take possession of the empty shell of some snail, and 
the protected abdomen becomes soft and flabby, while the 
appendages in this region almost completely disappear. 
The front part of the body, on the other hand, continually 
grows in firmness and strength, and is admirably adapted 
for the continual warfare which these forms wage among 
themselves. As growth proceeds the necessity arises for a 
larger shell, and the crab goes “ house-hunting ” among the 
empty shells along the shore, or it may forcibly extract the 
snail or other hermit from the home which strikes its fancy. 
Many of the hermit-crabs enjoy immunity from the 
attacks of their belligerent relatives by allowing various 
hydroids to grow upon their homes. Others attach sea- 
anemones to their shells or to one of their large claws, 
