CEEATA OF DENDB0N0TUS. 231 



which he says do not pass into the same sheath. I have, 

 therefore, examined with particular care the sections 

 concerned in this junction, and carefully noted any acces- 

 sory evidence with regard to the surroundings, shape, 

 conformation and other particulars seen in both sections 

 (figs. 8 and 9), and which help in any way to define exactly 

 the relations of the two nerves. There is a piece of con- 

 nective tissue, marked with an asterisk, in fig. 8 just 

 above the thin, but still distinct partition separating the 

 two nerves (a and c) at this point. In fig. 9 this piece 

 of connective tissue, of exactly the same shape and 

 relative position is present, and so marks exactly the point 

 where in the previous section the partition existed, but 

 which has here completely disappeared. There is no 

 doubt that the branch nerve (d), arising as it does from 

 a, looks, when viewed by dissection only, like the con- 

 tinuation of a, and that the nerve a + c. also when so 

 viewed looks like the continuation of c, and it is not 

 surprising that the mistake has been made of supposing 

 the junction merely a juxtaposition and not a union of 

 nerves. But when subjected by means of thin serial 

 sections to the higher powers of the microscope, it 

 obviates any chance of making errors of observation of 

 this character, and such a study of my sections convinces 

 me that the fibres of the branch c pass into, and are 

 enclosed in the same sheath as a, and therefore that the 

 lateral epipodial nerve contains both pleural and pedal 

 elements, as originally stated by Prof. Herdman and 

 myself. 



Explanation of Plates. 



Keference letters : — PI. XIV., a, auricle ; c', first pair of 

 cerata; c", second pair of cerata ; coe, coelome ; cs, 



