230 TEANSACTIONS .. LIVEEPOOL BIOLOGICAL SOCIETY. 



. In fig. 5, taken from the fourth section in the series 

 after fig. 4, the branch c is seen some distance from b 

 although not completely separated, there being a remnant 

 of connective tissue present. But it is much nearer the 

 nerve a and also connected with it by connective tissue. 



Fig. 6, taken from the next section, shows the pedal 

 branch c absolutely separated from b, and in close 

 connection with a, although still surrounded by its own 

 sheath. But the nerve a is here seen to be giving rise 

 to a branch d. The next section (fig. 7) shows this 

 branch divided off by a complete sheath, so that here 

 there are sections across three nerves (a, d and c) which 

 are in organic connection, but the fibres of each are 

 completely separated by clear and distinct sheaths. They 

 remain in much the same relation to each other through 

 the following three sections. But in the next section 

 (fig. 8) a and c come into closer relation, there is a 

 common investing sheath, while the portion of the peri- 

 neurium between the two has become thinner and less 

 pronounced ; and in the next section (fig. 9) it breaks 

 down altogether and the two nerves unite, the fibres of 

 the branch c becoming common, and enclosed in the 

 same sheath as a. There are seen now but two nerves, 

 the upper (d), a branch from a, and the lower, formed of 

 the remainder of a plus the fibres of the nerve c, which 

 is a branch from the dorsal pedal nerve b. The nerve a 

 arises from the pleural ganglion and therefore contains 

 pleural elements, while c is a branch of the pedal nerve b, 

 which arises from the pedal ganglia, and contains pedal 

 elements, and therefore the resulting nerve (a-\-c) contains 

 both pleural and pedal elements. 



The crucial point is evidently at the junction of a and 

 c, as these are the two nerves which Pelseneer admits 

 come into contact with each other, but the fibres of 



