230 COMPARATIVE ZOOLOGY. 
is of the family Cervidw, genus Cervus, species Virgini- 
anus, if the common Deer is meant. 
The following diagram roughly represents (for the rela- 
tions of animals can not be expressed on a plane surface) 
the relative positions of the subkingdoms and classes ac- 
cording to affinity and rank. It will be seen that the Ver- 
tebrate, Articulate, and Molluscan types stand at the angles 
of an isosceles triangle. The lowest Worms are simpler 
than the lowest Mollusks; yet Articulates, on the whole, 
are, perhaps, higher than the Mollusks: the former have 
more outward expression ; the latter, more concentration.* 
Mammalia. 
Aves. 
VERTEBRATA. me 
Reptilia. 
Amphibia. 
Pisces. 
Cephalopoda. Insecta. 
Gasteropoda. Myriapoda. 
Lamellibranchiata. Moiiusca. ArticuLaTa. Arachnida. 
Tunicata. Crustacea. 
Polyzoa. Brachiopoda. Annelida. 
Echinoidea. Holothuroidea. 
EcHINODERMATA. 
Asteroidea. 
Crinoidea. 
Anthozoa. 
Ca@LENTERATA. 
Hydrozoa. 
Spongida. 
Infusoria. 
PROTOZOA. 
Rhizopoda. 
Gregarinida. 
* The student should master the distinctions between the great groups, or 
classes, before proceeding to a minuter classification. ‘‘ The essential mat- 
ter, in the first place,” says Huxley, ‘‘is to be quite clear about the different 
classes, and to have a distinct knowledge of all the sharply definable modifi- 
cations of animal structure which are discernible in the Animal Kingdom.” 
