SEA-ACORNS. 



5 



widely different animal from the acorn itself. In the 

 days of its infancy the sea-acorn appears as a minute 

 oval body, possessing a single eye. A shell covers 

 its back ; a tail appears ; and from the front of the 

 body there grows a pair of feelers, while from its 

 sides project two pairs of legs. Internally a digestive 

 system soon appears ; and, thus provided, the young 

 acorn swims merrily through the sea. Then comes 

 the moulting stage. 



Increase of growth is impossible to a shelled animal 



Fig, 3. Development of Crustaceans. 



A and B are stages in Barnacle development : C and D are stages in the 

 development of a lower member (Sacculina) of the Crustacean class. 



unless the old shell be changed for a new one. 

 Hence the reason for the moults which the infant 

 animal exhibits. By-and-by, a further stage is reached 

 when the young acorn attains a still more perfect 

 shell composed of two distinct halves or pieces. The 

 front pair of feelers (a B) have increased in size ; but 

 the two original pairs of legs have been cast off, and 

 are replaced by six pairs of short, jointed feet. The 

 tail also develops swimming appendages ; and two 



