556 



Marvels of the Universe 



THE ACORN BARNACLE. 



[ir. /(. Johnson. 



A beautiful photograph of a group of the common species on a mussel shell. 

 Each individual is displaying his feathery tentacles in search of food. 



with every species, one variety, 

 such as the Ship Barnacle, having 

 only five component parts, while 

 another may have as many as forty 

 different valves ; but, in reality, 

 these smaller valves are only 

 sub-divisions of the larger masses, 

 and can be grouped into the 

 larger divisions, and hold exactly 

 the same relative position ; so 

 that even the valves in the Acorn 

 Barnacle, which in appearance is 

 totally unHke the Ship Barnacle, 

 occupy the same position as those 

 on its more conspicuous relation ; 



while the forms and varieties of even a single species are numberless and of great divergence. 



For instance, a specimen of the common Acorn Barnacle has been found with the shells narrow and 



elongated and snowy white, about 

 an inch and a half long, form- 

 ing a roughly shaped tube, and 

 totally unlike the usual form. 

 Again, Darwin has grouped a num- 

 ber of the shells of the Amphitrite 

 Barnacle which vary in every 

 conceivable way, with colouring 

 ranging from pink markings to 

 purple or the appearance of onyx. 

 Of this species Darwin wrote : 

 " After studying such varying 

 forms ... it is difficult to avoid, 

 in utter despair, doubting whether 

 there be such a thing as a 

 distinct species, or at least more 

 than half a dozen distinct species 

 in the whole gens of Acorn 

 Barnacles." 



This brings us to a consideration 

 of the two distinct types of Bar- 

 nacle : the Acorn Barnacle and 

 the Stalked Barnacle. Their chief 

 differences are in their general 

 appearance and their method of 

 living. The Stalked Barnacle has 

 been better equipped by Nature 

 for the development of its species 

 than the Acorn. It usually attaches 

 itself to floating objects, and is 

 further enabled, by means of its 

 long stalk, which will attain a 



Photo 6t(] 



This bunch 

 washed up on th< 



size.) 



[E. Step, F.L.S. 

 SHIP BARNACLES. 



f Barnacles is attached to the corlt of an empty beer-bottle 

 Cornish coast. (Reduced to about one-half tke actual 



