INVERTEBRATA. 393 



of science. This instrument (the microscope) is destined 

 to realize the dream of the naturalist, in the registering of 

 organic forms, and now stands the great sub-soil plough in 

 the realms of knowledge intelligible to the senses of man. 



The following classification of invertebrate animals is 

 used by Yon Siebold and Stannius in their " Comparative 

 Anatomy of the Invertebrata," translated from the German 

 by Waldo I. Burnett, of Boston. 



ANIMALIA EVERTEBRATA. 



INVERTEBRATE ANIMALS. 

 Brain, spinal cord, and vertebral column, absent. 



FIRST GROUP. 



PROTOZOA. 



Animals in which the different systems of organs are not 

 distinctly separated, and whose irregular form and simple 

 organization is reducible to the type of a cell. 



CLASS I. INFUSORIA. 

 CLASS II. RHIZOPODA. 



SECOND GROUP. 



ZOOPHYTA. 



Animals of regular form, and whose organs are arranged 

 in a ray-like manner around a centre, or a longitudinal axis ; 

 the central masses of the nervous system forming a ring, 

 which encircles the oesophagus. 



CLASS III. POLYPI. 

 CLASS IV. ACALEPH^S. 



CLASS V. ECHINODERMATA. 



THIRD GROUP. 



VERMES. 



Animals with an elongated, symmetrical body, and whose 

 organs are arranged along a longitudinal axis ; so that right 

 and left, dorsal and ventral aspects may be indicated. 



