348 



WILLIAM PATTEN. 



brain region, (4) its remarkable complex structure, as well as 

 the development of its nerves and sense-organs, — all invite a 

 detailed comparison of the oesophagus and fore-brain of 

 Arachnids with the fore-brain and hypophysis of Vertebrates. 



-'^P-^- 



ep'g- 



Fig. 11. — The fourth vagus and first abdominal neuromeres of Scorpion, 

 seen from the neural surface. — A. Stage f. B. Stages g, ii. Bj 

 comparing with figs. 1-4 in the Plates we see how the parts of the 

 primitive double neuromeres have recombined to form new ones. a. n^~-. 

 First and second abdominal neuromeres, </. m. c. Ganglionic portion of 

 median furrow, sp.ff. Spinal ganglia, sj}. n. Spinal nerve, v.n*. Fourth 

 vagus neuromere. T. Tail. 



The arguments in favour of supposing that the infundibulum 

 cerebri represents an Arachnid oesophagus with its nerves are 

 much stronger, I believe, than those advanced by Beard in 

 favour of his view. (1) Since in most Arachnids the oeso- 

 phagus is very small, owing to their blood-sucking habits, and 

 the canal for its passage through the brain is extremely small, 

 the Arachnid theory can give some explanation of how and 

 why the old mouth has disappeared. (2) In Limulus and 

 Scorpio two large parallel nerves extend along the whole 

 length of the sides of the oesophagus. Each nerve arises from 

 a thickening, which persists for a long time, of the distal 

 end of the oesophagus. As the latter increases iu length. 



