In the woodcut, the dots represent orders, the names of which it is impracticable to insert. If it be supposed that when magnified, each of these dots resolves itself into a cluster of clusters, representing genera and species, an approximate idea will be formed of the relations among the successively-subordinate groups constituting the animal kingdom. Besides the subordination of groups and their general distribution, some other facts are indicated. By the distances of the great divisions from the general centre, are rudely symbolized their respective degrees of divergence from the form of simple, undifferentiated organic matter; which we may regard as their common source. Within each group, the remoteness from the local centre represents, in a rough way, the degree of departure from the general plan of the group. And the distribution of the sub-groups within each group, is in most cases such that those which come nearest to neighbouring groups, are those which show the nearest resemblances to them--in their analogies though not in their homologies. No such scheme, however, can give a correct conception. Even supposing the above diagram expressed the relations of animals to one another as truly as they can be expressed on a plane surface (which of course it does not), it would still be inadequate. Such relations cannot be represented in space of two dimensions, but only in space of three dimensions. _Mammalia_ _Aves_ _Reptilia_ VERTEBRATA \ _Amphibia_\ _Pisces_ \ \ _Arachnida_ \ _Insecta_ \ _Crustacea_ \ \ Articulata \ | \ | _Myriapoda_ \ | \ ANNULOSA \ | \ |_Annelida_ \ _Scolecida_ \ | \ Annuloida \ | / \ _Echinodermata_ \ | / _Pteropoda_ _Cephalopoda_\ | | _Gasteropoda dioecia_ | | _Gasteropoda monoecia_ _Pulmonata_ | | \ | | MOLLUSCA------------- \ | | \ \ | | _Lamellibranchiata_ \ \ | | \ \ | | _Brachiopoda_ \ \ | | \ \ _Gregarinida_ Molluscoida------------ _Rhizopoda_ \