22 THE FIVE GEEAT BRANCHES. 



wth the sponges. So that the great Branches or Types 

 or Sub-kingdoms of the Animal Kingdom are : 



I. YERTEBRATA, 



Including all animals which have an internal jointed skeleton, 

 and a brain and spinal cord along the dorsal side ; as Man and other 

 Mammals, Birds, Reptiles, Batrachians, and Fishes. 



II. ARTICULATA, 



Embracing all animals which have the body made up of a series of 

 rings or joints, with the hard parts, when present, outside, and the 

 nervous centers mainly on the ventral side ; as Insects, Lobsters, 

 Worms, etc. 



III. MOLLUSCA, 



Comprising all animals which have a soft body inclosed in a mus- 

 cular sac, witli or without a shell, and which are neither jointed nor 

 radiated in their structure ; as Cuttle-Fishes, and Squids, Snails, Clams, 

 Oysters, etc. 



IY. RADIATA, 



Including all animals which have a radiated or star-shaped struc- 

 ture ; as Star-Fishes, Jelly-Fishes, Sea-Anemones, etc. 



Y. PROTOZOA, 



Including all animals which are not constructed according to the 

 plan exemplified in any of the four preceding branches ; as Infusoria, 

 Sponges, and Rhizopods. 



Of the five great Branches enumerated above, the Pro- 

 tozoans are the lowest, and the Yertebrates the highest. 

 Of the four besides the Protozoans, the Radiates are the 

 lowest. As to the two groups Mollusks and Articulates, 

 it is not easy to say which, on the whole, is the higher ; 

 although the higher rank is generally accorded to the Ar- 

 ticulates. 



In order to express the relations of these great groups, 



