CRUSTACEA OF THE SEASHORE 115 



day ; but the valves which close the opening of the 

 shell fit so tightly that a little sea-water is enclosed, 

 and the animal is protected from drying up even when 

 exposed to the heat of the sun. If a stone or a chip 

 of rock, with a few of these animals on it, be placed 

 in a jar of sea-water, their peculiar mode of obtaining 

 food can easily be watched. The valves will presently 

 be seen to open a little, and the curled cirri will be 

 protruded, opened out like the fingers of a hand, 

 and withdrawn again with a sort of grasping motion. 

 These movements are continued without stopping 

 while the animal is under water. If the cirri be 

 examined with a pocket-lens or under a microscope, 

 it will be seen that they are fringed with stiff bristles, 

 so that, when they are opened out, the whole forms 

 a kind of " casting-net." As it is swept through the 

 water, this net entangles minute floating particles of 

 animal or vegetable matter, and carries them into 

 the shell, so that they can be seized by the jaws and 

 swallowed. The cirri, as we have already seen, are 

 really the modified thoracic limbs, so that, in Huxley's 

 words, " A Barnacle may be said to be a Crustacean 

 fixed by its head, and kicking the food into its 

 mouth with its legs." 



A mode of obtaining food by " net-fishing," not 

 unlike that employed by the Barnacles, is found in 

 certain Crustacea belonging to a widely different 

 group the little "Porcelain Crabs" (Fig. 41) 

 mentioned above. Mr. Gosse observed that the 



