GROWTH. 137 



growth, is, that it has limits. Here there appears to be a 

 distinction between organic and inorganic growth; but thi-s 

 distinction is by no means definite. Though that aggrega- 

 tion of inanimate matter which simple attraction produces, 

 may go on without end; yet there appears to be an end to 

 that more definite kind of aggregation which results from 

 polar attraction. Different elements and compounds habitu- 

 ally form crystals more or less unlike in their sizes ; and each 

 seems to have a size that is not usually exceeded without a 

 tendency arising to form new crystals rather than to increase 

 the old. On looking at the organic kingdom as a 



whole, we see that the limits between which growth ranges 

 are very wide apart. At the one extreme we have monads 

 so minute as to be rendered but imperfectly visible by micro- 

 scopes of the highest power; and at the other extreme we 

 have trees of 400 to 500 feet high and animals of 100 feet 

 long. It is true that though in one sense this contrast may 

 be legitimately drawn, yet in another sense it may not ; since 

 these largest organisms arise by the combination of units 

 which are individually like the smallest. A single plant of the 

 genus Protococcus, is of the same essential structure as one of 

 the many cells united to form the thallus of some higher 

 Alga, or the leaf of a phaenogam. Each separate shoot of a 

 phasnogam is usually the bearer of many leaves. And a 

 tree is an assemblage of numerous united shoots. One of 

 these great teleophytes is thus an aggregate of aggregates of 

 aggregates of units, which severally resemble protophytes in 

 their sizes and structures ; and a like building up is traceable 

 throughout a considerable part of the animal kingdom. 

 Even, however, when we bear in mind this qualification, and 

 make our comparisons between organisms of the same degree 

 of composition, we still find the limit of growth to have a 

 great range. The smallest branched flowering plant is ex- 

 tremely insignificant by the side of a forest tree; and there 

 is an enormous difference in bulk between the least and the 

 greatest mammal. But on comparing members of the 



