ORGANIC DEPENDENCE AND DISEASE 
61 
Fig. 50. A colony of the coral Favosites niagarensis which has partially overgrown 
a small plantation of the cyathophylloid coral Amplexns. From the Niagara 
formation (Silurian), Monticello, Iowa, x y 2 . 
THE BARNACLES 
It is well known that the barnacles are degenerate and 
attached crustaceans. The acorn barnacle with its hard 
valves consolidated into a cone-shaped shell, and the goose 
barnacle with its flat shells on clustered steins, represent 
for us the living members of this interesting group of 
recreants . 1 In the barnacle, of whichever kind, the animal 
has lost its independence through attachment by its head 
or back and the readjustment of its segmental plates to tit 
the demands of its stationary maturity. Ontogeny shows 
a free and normal larval state for the barnacle and indi- 
cates a phytogeny in which locomotive independence had 
been normal throughout life. 
We have known for some years the existence of barnacles 
in the Paleozoic rocks. The acorn barnacle Palaeocreusia, 
i Far greater degeneration of anatomy and function is presented by several 
other forms of soft-bodied barnacles in existing seas. 
