14 
ORGANIC DEPENDENCE AND DISEASE 
iology than the oyster and very rarely attached solidly to 
the sea bottom, yet the same degenerative effect npon the 
animal has been produced by burying itself in the mud with 
only the tips of the valves or a pair of fleshy tubes extruded 
upward to reach the moving food supply in the water cur- 
rents, while the burial helps out in large measure the de- 
fensive purpose of the solid armature of the shell. The 
clam is a much older creature than the oyster and in specific 
functions it has, broadly speaking, degenerated less, but it 
serves to bring out the important fact that the habit of 
burial in the mud, from which it does not easily release it- 
self and never for long, is tantamount to fixation and in- 
volves the organic stagnation in which these creatures have 
lain for ages which can not be counted. This is hardly the 
place in which to restate well-known paleontological facts, 
but such cases as these and the extensive catalog of like in- 
stances must serve to remind us that such adjustments, 
early formed and perdu ring through the ages, have been 
attended with the least possible variation in proportion as 
the adjustment is perfect. The longest lived of all crea- 
tures, then, are those which have lived in most perfect 
adjustment and in which therefore readjustment is most 
hopeless. 
We have very direct evidence of the early formation and 
long endurance of specific habits of life in these adjusted 
dependents. The starfish of the Devonian age fed upon con- 
temporary mollusks in the same way and by the same mode 
of attack that the starfish uses today upon the oysters of 
Long Island sound; surrounding the tightly closed valves 
with their strong-armed rays, pulling steadily against the 
strained muscle contraction of the mollusk until the weary 
shell-fish, muscularly tired out, gives up, the valves relax 
and open and the extrusive maw of the radiate enters . 1 
i Clarke. Jour. Acad. Nat. Sci., Philadelphia, v. 15, 2d ser. Centenary num- 
ber. 
