GROWTH. 139 



extreme small grasses and at the other tall palms, show us an 

 average and a maximum greater than that reached by the 

 Pteridophytes. And the Monocotyledons are exceeded by 

 the Dicotyledons; among which are found the monarchs of 

 the vegetal kingdom. Passing to animals, we meet 



the fact that the size attained by Vertebrata is usually much 

 greater than the size attained by Invertebrata. Of inverte- 

 brate animals the smallest, classed as Protozoa, are also the 

 simplest; and the largest, belonging to the Annulosa and 

 Mollusca, are among the most complex of their respective 

 types. Of vertebrate animals we see that the greatest are 

 Mammals, and that though, in past epochs, there were Rep- 

 tiles of vast bulks, their bulks did not equal that of the 

 whale: the great Dinosaurs, though as long, being nothing 

 like as massive. Between reptiles and birds, and between 

 land-vertebrates and water-vertebrates, the relation does not 

 hold : the conditions of existence being in these cases widely 

 different. But among fishes as a class, and among reptiles as 

 a class, it is observable that, speaking generally, the larger 

 species are framed on the higher types. The critical 



reader, who has mentally checked these statements in pass- 

 ing them, has doubtless already seen that this relation is 

 not a dependence of organization on growth but a dependence 

 of growth on organization. The majority of Dicotyledons 

 are smaller than some Monocotyledons; many Monocotyle- 

 dons are exceeded in size by certain Pteridophytes; and 

 even among Thallophytes, the least developed among com- 

 pound plants, there are kinds of a size which many plants of 

 the highest order do not reach. Similarly among animals. 

 There are plenty of Crustaceans less than Actiniae; nume- 

 rous reptiles are smaller than some fish; the majority of 

 mammals are inferior in bulk to the largest reptiles ; and in 

 the contrast between a mouse and a well-grown Medusa, we 

 see a creature that is elevated in type of structure exceeded 

 in mass by one that is extremely low. Clearly then, it cannot 

 be held that high organization is habitually accompanied by 



