320 MANUAL OF NATURAL HISTORY. 



III. SUB-ORDER. AMPHIPOKINES (Amphiporina). 



Oral and anal apertures terminal, at opposite ends 

 of the body. 



6. FAMILY. Gyratrices (Gyratricidse). No dis- 



tinct genital aperture ; body tapering ; blind, 

 or with numerous eyes. 



7. FAMILY. Nemertides (Nemertidse). A distinct 



anterior genital aperture ; body filiform, soft, 

 often depressed ; blind, or with a simple 

 series of frontal eyes. 



SUB-KINGDOM OF RAD I ATE- ANIMALS. 



Constructed on a widely extended principle of 

 nature, namely, radiation from a central point, the 

 classes of this Sub-kingdom exhibit extremely 

 simple forms of distinctive animal life. In the 

 lower grades, the growth is unlimited and plant- 

 like, and the digestive cavity possesses only a 

 single terminal orifice, surrounded by tentacles ; 

 in the higher forms, however, the alimentary sys- 

 tem is more complex, and the anal orifice becomes 

 separated from the oral. Usually the nervous sys- 

 tem is distinctly present in the form of a ring sur- 

 rounding the oesophagus, which gives off filaments 

 in a radiate manner to supply the different parts of 

 the body; the senses are usually but feebly deve- 

 loped, little more than touch and taste having been 



