THE PRINCIPLES OF BIOLOGY. 
289 
THE PRINCIPLES OF BIOLOGY. 
BY HERBERT SPENCER. 
Exposition of Part IV., Chapters V. and VI. 
“ The Morphological Composition of Animals.” 
[Abstract.] 
BY W. R. HUGHES, F.L.S. 
Iii the opening sentence of the first of these two 
remarkable chapters Mr. Herbert Spencer directs attention 
to a previous section of the work (§ 180 ), and points out 
tliat “ what was said respecting the ultimate structure of 
organisms holds more manifestly of animals than of plants.” 
It will, therefore, be useful to quote this section almost in its 
entirety. 
He says, in discussing the “morphological unit”:— 
“ Supposing that clay were the only material available for 
building, the proposition that all houses are built of bricks, 
would bear about the same relation to the truth, as does the 
proposition that all organisms are composed of cells. This 
generalization respecting houses would be open to two 
criticisms: First, that certain houses of a primitive kind are 
formed, not out of bricks, but out of unmoulded clay; and 
second, that though other houses consist mainly of bricks, yet 
their chimney-pots, drain-pipes, and ridge-tiles do not result 
from combination or metamorphosis of bricks, but are made 
directly out of the original clay. And of like natures are the 
criticisms which must be passed on the generalization, that 
cells are the morphological units of organisms. To continue 
the simile, the truth turns out to be, that the primitive clay 
or protoplasm out of which organisms are built, may be 
moulded either directly, or with various degrees of 
indirectness, into organic structures. The physiological units, 
which we are obliged to assume as the components of this 
protoplasm, must, as w T e have seen, be the possessors of those 
complex polarities which result in the structural arrangements 
of the organism. The assumption of such structural arrange¬ 
ments may go on, and, in many cases, does go on, by the 
shortest route; without the passage through what we call 
metamorphoses. But where such structural arrangements 
