6 9 



CHAPTER VI. 



TRACES OF UNITY IN THE ANIMAL AS A 

 WHOLE. 



THE body and its appendicular organs agree in being 

 made up of segments, and the segments themselves do 

 not disagree as much as they would seem to do at first 

 sight. Thus, the annelli of the tail of a scorpion are 

 intermediate between those of the body and those of the 

 limbs. Thus, the vertebrae of the tail of a cat are inter- 

 mediate between the vertebrae of the body and the 

 bones of the different segments of the limbs. There are 

 numberless differences between the segments of the 

 body and those of its appendicular organs in these arid 

 other cases, but none that are in any measure irrecon- 

 cileable. There are none so great as those which exist 

 between the segments of the body and those of the 

 head ; and even the presence of a visceral system in the 

 segments of the body, which may be looked upon as the 

 chiefest of all differences, is done away, not only in the 

 ray of the starfish, but also in the legs and great oral 

 palps of many arachnidans. Indeed, it is impossible to 

 look attentively at the arachnidan parasite of the whale 

 without being convinced that the presence of a visceral 

 system is not to be regarded as distinctive of the seg- 

 ments of the body. For here, as in the starfish, the 

 cavities within the limbs communicate directly with the 

 visceral cavity of the body, and are occupied throughout 



