902 The American Naturalist. [October 
ence of consciousness, or the experience of pleasures and pains, 
as consequences of movements. The movements are first per- 
formed under the experience of the necessity of securing the one, 
and of avoiding the other; a desire which is a condition of con- 
sciousness wherever it exists. Another objection to the explana- 
tion of the origin of designed acts by fortuity and natural selec- 
tion, is identical in character with that which has been urged 
against the similar explanation of the origin of permanent varia- 
tions of structure. The chance of the accidental performance of 
profitable movements among all possible movements, is very 
small; and the chance of the repetition of such movements by a 
sufficiently large number of individuals to cause them to be pre- 
served by reproduction and inheritance is much smaller. In order 
to preserve such movements so that they should become habitual 
in a single individual, it would be necessary they they should be 
performed by it frequently,—a probability which diminishes 
directly in proportion to the frequency required to produce that 
result. Thus our negative knowledge of this subject agrees with 
our positive knowledge in impressing us with the extreme im- 
probability of a single habitual designed act having arisen and 
been perpetuated by chance. | 
It is sometimes doubted whether consciousness can exist in 
such simple beings as the Protozoa. But this doubt seems to be 
unnecessary after a consideration of the organization of such 
higher forms of life as we know to be conscious. The higher 
multicellular animals, or Metazoa, consist of a colony of cells 
which display different degrees of specialization for the perform- 
ance of the different functions to which evolution assigned them. 
Their degree of specialization is of course measured by their 
degree of departure from the simple, primitive nucleated cells 
from which they have been derived by descent. Perhaps the 
most specialized are those which have become the threads of the 
connective and elastic tissues, and those of the tendons. Those 
of the modified epithelial tissues which cover the integument of 
the body, with its appendages, as scales, nails, horns, and hairs, 
are also highly modified. Muscular tissue is a little less specialized. 
In none of these tissues do we find consciousness. It is not cer- 
