1892.] i Conflict Between Organisms. 927 
or other organism at some point o in space, where the sur- 
roundings render mimetic coloration useful and where such 
surroundings now have tints so like the organism itself as to 
amount to positive and absolute concealment so long as the 
organism is — In this case accessibility to enemies 
again sinks to zero 
Parasites also are s protected not only by virtue of their con- 
cealment within their hosts but also by the possible mimetic 
coloration of the latter. 
Recapitulating, our series gives us the following comparative 
values : 
For organisms swimming in water or flying in air, we may 
say that their accessibility inter se and liability to attack is 
from 60,000 directions. 
For sessile organisms or those lying on a plane, their accessi- 
bility inter se and liability to attack is from 30,000 directions. 
For heavy terrestrial forms their accessibility inter se and 
liability to attack by their fellows is from 400 directions. 
For burrowing or tubicolous forms accessibility sinks to any 
where from 314 to 0 directions of approach 
For testaceous, operculate, mimetic or parasitic forms accessi- 
bility to enemies sinks to almost or quite 0. 
That the intensity of the struggle for existence under the 
diverse conditions supposed varies as greatly as is indicated by 
the figures seems to be in a great measure supported by the 
facts of adaptations. For example, the high specialization of 
flying and free-swimming organisms must at once appeal to 
us in verification of the preceding statement. The high tem- 
perature of birds, the pneumaticity and specialization of their 
skeletons ; the somatic, tracheal respiration and relatively high 
temperature of the bodies of flying arthropoda is proof of the 
high rate at which energy is dissipated and the effectiveness 
of the mechanism through which such dissipation is effected. 
Similarly, it may be-said that only the free swimming types 
of fishes, such as the herrings, mackerels, sharks, etc., are 
“clipper built ” for high velocities of motion while those that 
depend upon stealth, concealment for the capture of their prey 
and escape from enemies, are either depressed in form or even 
