SECT. V THE NERVOUS SYSTEM 71 



would be affected by this splitting of the oesophageal 

 commissure owing to the travelling backwards ^ 

 of the brain. Taking first the case illustrated in Fig. 

 19, i.e., assuming that the nerves for the first antennae 

 branched, in the original Annelid, from the first 

 ventral ganglia, we tried to answer this question 

 theoretically. Our answer, however, was not quite 

 correct. We assumed that the first antennal nerve was 

 originally united with the oesophageal commissures for 

 a short distance, and would remain where it was when 

 the brain dragged away the portion it required for 

 itself We were doubtless also misled by the position of 

 the first antennae of Apus near the prostomium. These 

 mistakes were very natural. For the second antennae, 

 however, our answer was correct. We rightly assumed 

 that as the brain and oesophageal commissures moved 

 forwards and upwards, passing through the position 

 occupied by these antennal nerves, the two might 

 unite, so that we described the nerves for the second 

 antennae as branching off from the brain commissures, 

 this position agreeing best with the position of the 

 second antennae in Apus. 



On comparing this theoretical scheme for the antennal 

 nerves with Zaddach's drawings, we found, as stated, 

 that the nerve for the first antenna, which has the 

 more ventral position, branched off from the brain- 

 oesophageal commissure dorsally to the nerve of the 

 second antennae which has the more dorsal position, 

 so that, if Zaddach's drawings were correct, a slight 



^ " Backwards " is morphologically correct ; actually the brain moved 

 forwards and upwards. 



