172 RAMBLES OP A NATURALIST. 



was in the act of producing the posterior segments of 

 the body, which had been lost by some accident, but 

 no adult animal had hitherto been met with which 

 presented any very apparent traces of this original 

 division. In the Hermella, however, this division 

 exists throughout the greater portion of the body. 

 Throughout the whole length of the abdomen, the 

 muscles, vessels, and nerves are all double, and the 

 two halves are only held together by the skin and by 

 the digestive canal, which is single. Here, then, the 

 Annelid is actually cleft in two; both before and 

 behind all parts of the muscular and vascular appa- 

 ratus meet along the middle of the body, but the 

 ventral nervous system remains divided from the one 

 extremity to the other, and its two halves only com- 

 municate together by delicate threads or excessively 

 thin bands.* 



At the period when I made these observations, this 

 division of the nervous system in the Hermellas was 

 regarded as an entirely exceptional mode of arrange- 

 ment ; but in the course of my investigations I found 

 that the Annelids exhibited many other equally re- 

 markable phenomena. This is incontestably the most 

 interesting group to which the zoologist can at the 

 present day devote his attention ; for it appears to be 



* I would here observe, that in the Articulata the principal 

 nervous centre is situated in the head above the digestive tube. 

 This ganglion is considered as the representative of the brain in the 

 Vertebrata, because it usually furnishes nerves to the organs of the 

 senses. This brain is united by two connecting filaments to the 

 abdominal nervous system, which is placed below the digestive tube, 

 and consists essentially of a chain of nervous centres or ganglia 

 united by other connecting filaments. 



