354 ESSAY ON CLASSIFICATION. 



organic functions of life are carried on in antagonistic 

 relations, from the centre to the circumference. Corre- 

 sponding to this, the whole organization radiates around 

 a common centre. There exists, besides, only the contrast 

 between above and below, but in a weaker degree ; that 

 between right and left, or before and behind, is not at all 

 noticeable, and the motion is therefore undetermined in 

 its direction. As the whole organization radiates from 

 one focus, so are the centres of all the organic systems 

 arranged, ring-like, around it; as, for instance, the sto- 

 mach, the nerves and the vessels (if these parts are deve- 

 loped), and the branches extending from them into the 

 rays. What we find in one ray is repeated in every other, 

 the radiation being always from the centre outwards, and 

 every ray bearing the same relation to it. 



II. The Longitudinal Type, as observed in the Vibrio, 

 the Filaria, the Gordius, the Nais, and throughout the 

 whole series of articulated animals. The contrast between 

 the receiving and the discharging organs, which are placed 

 at the two ends of the body, controls the whole organiza- 

 tion. The mouth and the anus are always at opposite 

 ends, and usually also the sexual organs, though their 

 opening is sometimes farther forward : this occurs, how- 

 ever, more frequently in the females, in which these organs 

 have a double function, than in the males. When both 

 sexual organs are removed from the posterior extremity, 

 the opening in the female usually lies farther forward than 

 in the male. So is it in the Myriapods and the Crabs. 

 The Leeches and Earthworms present a rare exception. 

 The receptive pole being thus definitely fixed, the organs 

 of senses, as instrumental to the reception of the ner- 

 vous system, early reach an important degree of perfec- 

 tion. The intestinal canal, as well as the vascular stems 



