644 EEPOET— 1880. 



nervous system. I ought not, however, to leave this subject ■without saying a few 

 words as to the hypothetical view? which the distinguished evolutionist Mr. Herbert 

 Spencer has put forward on this subject in his work on Psychology. 



For Herbert Spencer nerves have originated, not as processes of epithelial cells, 

 but from the passage of motion along the lines of least resistance. The nerves would 

 seem, according to this view, to have been formed in any tissue from the continuous 

 passage of nervous impulses through it. ' A wave of molecular disturbance,' he 

 says, ' passing along a tract of mingled colloids closely allied in composition, and 

 isomerically transforming the molecules of one of them, will be apt at the same 

 time to form some new molecules of the same type,' and thus a nerve becomes 

 established. 



A nervous centre is formed, according to Herbert Spencer, at the point in the 

 colloid in which nerves are generated, wliere a single nervous wave breaks up, and 

 its parts diverge along various lines of least resistance. At such points some of 

 the nerve-colloid will remain in an amorphous state, and as the wave of molecular 

 motion will there be checked, it will tend to cause decompositions amongst the un- 

 arranged molecules. The decompositions must, he says, cause ' additional molecular 

 motion to be disengaged ; so that along the outgoing lines there will be discharged 

 an augmented wave. Thus there will arise at this point something having the 

 character of a ganglion corpuscle.' 



These hypotheses of Herbert Spencer, which have been widely adopted in this 

 country, are, it appears to me, not borne out by the discoveries to which I have 

 called your attention to-day. The discovery that nerves have been developed from 

 processes of epithelial cells, gives a very diflerent conception of their genesis to 

 that of Herbert Spencer, which makes them originate from the passage of nervous 

 impulses through a tract of mingled colloids; while the demonstration that 

 ganglion-cells arose as epithelial cells of special sense, which have travelled inwards 

 from the surface, admits still less of a reconciliation with Herbert Spencer's view 

 on the same subject. 



Although the present state of our knowledge on the genesis of the nervous 

 system is a great ad\auce on that of a few years ago, there is still much remaining 

 to be done to make it complete. 



The subject is well worth the attention of the morphologist, the physiologist, or 

 •even of the psychologist, and we must not remain satisfied by filling up the gaps 

 in our knowledge by such hypotheses as 1 have been compelled to frame. New 

 methods of research will probably be required to grapple with the problems that 

 are still unsolved ; but when we look back and surA'ey what has been done in the 

 .past, there can be no reason for mistrusting our advance in the future. 



The following Papers were read :— 



1. On the Alkaline Fermentation of Urine. Bij A. S. Lea. 



2. On the Origin of the Head-Kidney. By A. Sedgwick, B.A. 



The hypothesis of Gegenbam- and Fiirbringer as to the relation of the head- 

 kidney to the hinder part of the excretory sj'stem was considered, the objections to 

 it pointed out, and the following hypothesis put forward. The head-kidney is the 

 anterior part of a primitive excretory organ possessed by some ancestral vertebrate, 

 the posterior part of which has persisted as the Wolffian body. In support of this 

 view it was pointed out that the structure of the head-lridney essentially resembles 

 that of the Wolffian body. It was further noticed that, though at first sight the 

 development of these two organs is entirely different, on a closer examination they 

 are found to present a development fundamentally similar. The development of 

 the Wolffian body in Amphibia and other animals with a head-kidney must be con- 



