4i8 CHARACTERS OF INVERTEBRATE ANIMALS 



flattened oval swelling, covered by a number of shelly pieces, 

 suggesting at first sight that the animal is a kind of Mollusc. A 

 closer examination will show that these pieces are attached to 

 a couple of soft flaps united together on one side, but leaving 

 between them on the other side a slit through which, in a living 

 specimen, a bundle of hairy-jointed filaments will from time to 

 time protrude and spread out, being drawn back again immediately 



afterwards. These tendril -like struc- 

 tures, or cirri, which act as a kind of 

 casting-net, whereby food is swept into 

 the mouth, are six pairs of bifurcated 

 appendages, and their jointed nature 



SCUTUM -i^^aai ''^*Ka> i i i i- • i 



shows that we are dealmg, not with a 

 Mollusc, but with an Arthropod. To 

 °""'^' a strong imagination they might sug- 

 gest feathers in a vague way, and they 

 Fig..59.-ship-B^nacies^(z.><z.a««/,>^a), ^j.g probably responsible for the well- 

 known natural-history legend, according 

 to which the Solan Goose ("Barnacle" Goose) develops from 

 a barnacle, the chicks falling into the water when sufficiently 

 grown to look after themselves. The specific name of the 

 barnacle, "anatifera" (L. anser, a goose; fero, I bear), has 

 reference to this old belief. On removing the shell, and the 

 flaps to which it is attached, the soft body of the animal will 

 be found, consisting mainly of thorax, to which the tendril-like 

 appendages are attached. The abdomen is reduced to a limbless 

 process ending in a long filament. The under (ventral) side of 

 the thorax is turned upwards, and at its front end will be found 

 the mouth, provided with upper lip, mandibles, and two pairs of 

 maxillae. No eyes or feelers are visible, but study of the develop- 

 ment shows that the animal is fixed by its head, which has grown 

 into a long stalk, at the end of which were situated the short 

 antennules, that served as organs of attachment from which the 

 sticky secretion of special " cement glands " was poured out. The 

 antennae, present in the larva, entirely disappear in the adult. 

 Huxley has graphically compared a barnacle to a man lying upon 

 his back and kicking his food into his mouth. 



Acorn-Barnacles agree essentially in structure with the ship- 

 barnacle, but do not possess a stalk, and there is an extra pro- 

 tection to the body in the form of a sort of shelly cup made up 



