Aiiiiloini/ of Jli/la amca. 357 



A'//.- -This is found in 3-1 per cent, of cases, as iiroviniisly 

 described, and only when XI. is larger than iisual. 



It will bo seen that I am still of the opinion that, so far 

 aa evidence shows up to date, the sacral plexus appears to be 

 niovinu' forwards, the ooccygeal nerve gradually diminishing in 

 phy.siological importamce, as previously shown by Adolphi ("93, 

 '95, '98 — ) and myself ('97—). Cole (p. 116) acknowledges the 

 fact that as " the vertebral axis shortens up from behind, for- 

 wards, to produce the complex known as the urostyle, sieveral of 

 the most posterior spinal nerves are eliminated in the process," 

 as shown by Adolphi (loc. cit. ). At the same time, he considers 

 that the sacral plexus is moving back — i.e., he apparently 

 believes that up to a certain stage a reduction of spinal nerves 

 in the sacral region takes place, followed in the next stage by an 

 addition of nerves in the same relative positions as were those 

 which harve been lost. Until we have much more definite 

 evidence of such an apparently uneconomical method of develop- 

 ment, either in the individual or the group, it is unnecessary to 

 imagine such a process. 



As to the statistical method employed by Adolphi and myself, 

 which Cule considers open to criticism, while agreeing that the 

 thickness of a nerve may not be an infallible guide as to its 

 physiological power, it appears to me^ — in the absence of direct 

 evidence to the contrary in the Amphibia — that it may be 

 accepted as an indication of probable importance. 



III. — Urinogenital System. 



Variations in the structui'e of this system ai*e very rare. In 

 one instance, found this year, there Avaa present on each side in 

 ai male frog, a medium-sized, well-formed oviduct. This ex- 

 tended from the funnel at the anterior end, as far as the middle 

 of the length of the kidney, where it ended abruptly. For the 

 greatest part of its length it coiled in the usual manner. The 

 two sides were similar. No trace of a " Bidders organ " could 

 bo found, and the vasa efferentia and fart Ijodies were normal. 

 From a surface exaiuinatiou the testes also appeared normal, 

 but a series of sections showed clearly the presence of 15-20 

 ova, scattered irregularly through the substance of the testes, 



