118 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



connected in any way with the sciatic plexus. It will be 

 noted that in this case also the latter plexus is postfixed, 

 and that the urostyle is a morphological compound of at 

 least three pieces.* On the left side the ixth nerve was the 

 stoutest, the others following in the order, 8, 10, 7. On 

 the right side, the nerves, similarly arranged, would read, 

 9, 10, 8, 7. The right xith nerve was appreciably 

 smaller than the left, and the left crural was stronger than 

 the right. In Hyla aurea Miss Sweet found an xith nerve 

 in 3'2 per cent, of 125 specimens examined, whilst in 

 Pipa Fiirbringer has shown that two pairs of spinal nerves 

 normally perforate the urostyle. 



The third case, also a R. esculenta, is complicated by the 

 occurrence of an abnormality in the vertebral column, 

 thus rendering the enumeration of the nerves a subject 

 for speculation. Unhappily one side of the specimen had 

 been too much damaged to be described here, although 

 it was apparently similar to the side figured. The first 

 point noticeable is that the nerve VI + takes no 

 part in the formation of the lumbo-sacral plexus, and 

 that the relative position of this plexus with regard to the 

 urostyle is quite normal, so that it has apparently dropped 

 a nerve in front without picking up one behind. But 

 there is a nerve present (viii.) which perforates the arch 

 of the compound sacrum, and bears the same relation to 

 the plexus as a normal viiith nerve. It therefore becomes 

 necessary to describe the sacrum. 



That the vertebra labelled T may be the eighth is 

 suggested by the fact that it is amphicoelous, and only 

 the eighth vertebra of the frog exhibits that character. 

 The urostyle is further no more or less than its normal 



* It must not be forgotten that in Bombinator, according to 

 Gotte, the urostyle represents 3 fused vertebrae — x., xi. and xii. 

 Cf. also the condition in Discuglossus. 



