SECTION VII 

 The Alimentary Canal 



Although it is not, as a rule, possible to draw 

 any conclusions as to the relationship between animal 

 groups from the similarity of their alimentary canals, 

 yet the likeness between the digestive tract of the 

 Apodidae and that of the Annelida is so striking 

 that it must be admitted to be of some weight in 

 establishing the relationship which this book seeks to 

 prove. Allowing for the bend in the oesophagus, 

 the alimentary canal runs straight through the body 

 from end to end, and the mid-gut is lined by the 

 thread-like ciliated epithelium characteristic of that 

 of the Annelida. 



The bending of the first five segments of our 

 Annelid, so that the mouth not only lies ventrally 

 but faces posteriorly, necessarily led to a bend in the 

 alimentary canal, so that, from the mouth, the 

 oesophagus would slope upwards and forwards. Wc 

 find that it has this position in the Apodidae, and 

 from the Apodidae it has been handed on to the 



