262 



THE SEA SHORE 



bodies by which they are carried about. Thus they are enabled to 

 find the food they can no longer seek without such aid. In their 

 young state they possess not only the means of freely moving in 

 search of their food, but have organs of vision to aid them in 

 the capture of their prey. As they grow, however, the foremost 

 appendages are transformed into a sucking-disc, and the eyes, no 

 longer necessary, disappear. It will thus be seen that the 

 degenerated adult the product of a retrograde development is 



FIG. 192. 



-FouB STAGES IN THE DEVELOPMENT OF 

 THE ACORN BARNACLE 



A, newly hatched larva ; B, larva after second moult ; C, side view of same : 

 D,. stage immediately preceding loss of activity ; a, stomach ; b, base of future 

 attachment. All magnified 



attached by what was originally the front of its body, while the 

 abdomen is undeveloped, and the thorax, with its appendages, forms 

 the summit of the free extremity. 



Some of the Cirripedes attach themselves to the bodies of 

 whales and other marine animals. The majority of these are 

 pseudo-parasites creatures that live on the bodies of other animals, 

 but do not derive their food at the expense of their hosts ; others, 

 however, are true parasites, subsisting on the nourishing juices they 

 extract from the animals to which they are attached. 



