116 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



by, or conducted according 1o, the findings of the com- 

 ponent theory." The " Spinal nerves" of the frog are in 

 this paper enumerated from before backwards, the hypo- 

 glossal, according to English custom, being considered 

 the first. I am, of course, aware that this nerve is 

 morphologically the second, the first or N. suboccipitalis, 

 present in the tailed amphibians, as shown by Furbringer, 

 occurring only in the embryo, according to Chiarugi. 



In the first case, a specimen of Bona temporaries, the 

 brachial plexus is normal enough on the right side, 

 according to Gaupp's scheme, but on the left side the third 

 nerve communicates in the very unusual way shown in 

 the figure. Nerves iv., v. and vi. are quite normal, but 

 the sciatic plexus is in a somewhat unique condition. 

 The presence of what I have identified as two iliohypo- 

 gastric nerves on the left side and of two crural nerves 

 on the right side may be noticed at once. That these 

 nerves may be duplicated has already been noticed by 

 Miss Sweet in Hyla a urea. The chief interest in the 

 specimen however lies in the condition of its coccygeal 

 nerve, which is very much larger than usual, and instead 

 of only more or less indirectly contributing towards the 

 sciatic plexus, passes wholly into it without the exception 

 of a single fibre. "Where the accessory coccygeal fibres 

 come from, and how the fibres in the different factors of 

 the plexus had been shuffled to produce this arrangement, 

 could of course only be determined by serial sections. 

 The ixth nerve, it will be noted, forms a loop before 

 uniting with, the plexus. This variation may be 

 explained in two ways. We know from the admirable 

 work of Adolphi that larval Anura, on metamorphosis, 

 lose a number of caudal spinal nerves. That is to say, 

 when the vertebral axis shortens up from behind forwards 

 *Cf. G, J. Herrick, Jour. Comp. Neurol, ix., 1G3 et sea. 



