36 
ORGANIC DEPENDENCE AND DISEASE 
basket (Euplectella) imprisons a crab in its interior behind 
the bars it throws across its aperture but feeds it with 
ever changing water currents ; worms and antliozoan corals 
grow together, with the tubes of the former surrounded by 
the cells of the latter, both sweeping the water currents 
for food which may go to either mouth ; dead snail shells 
in which hermit crabs have taken residence are often beset 
with sea anemones (Sagartia and Adamsia) whose stinging 
cells may scare away the enemies of the crab, while the crab 
favors the fixed anemones by moving his establishment 
from place to place, thus to new feeding grounds. 
All these conditions seem on the surface entirely harm- 
less or positively advantageous to all parties involved ; that 
is, advantageous in the sense that they make life easier, 
less arduous, discourage activity and perfect adaptation. 
The general effect of all symbiotic conditions is degenera- 
tive. They themselves arise from degenerate tendencies 
and could not exist save that degeneration had already set 
in. They are expressions of this condition and serve to 
confirm and transmit this tendency. The fact is tremen- 
dously evident that even the most innocent of symbiotic, de- 
pendent or attached conditions of growth is the leaven of 
progressive degeneracy. 
It is well known that the critical methods of morphology 
and embryology have been requisite to determine the origi- 
nal ancestral independence of the most debased of para- 
sites. While the doctors of the Middle Ages wondered over 
the barnacles and pictured them as growing on trees, drop- 
ping thence to the ground transformed into geese, their 
real nature as debased crustaceans was not unfolded till 
the life history of the creatures showed that their early 
stages were free and predatory, and the adult condition 
one of extreme adaptation by progressive loss of functions 
and organs. Thus the parasitic and dependent habit is, in 
metazoan life, preceded by a free and predatory condition. 
