128 / LIONEL TAYLER [august 



there is always a certain excess force, which would be fostered by 

 selection, sufficient to provide for emergencies. 



9. Rudiments and their disappearance. — It is assumed that there 

 will come a point where the rudiment ivill be of such slight significance 

 that it will no longer be of selection value, hence it is urged that the fact 

 that rudiments do tend to completely disappear, is against any purely 

 selectionist principle. Leaving out of consideration the possibilities of 

 reversal of selection, panmixia, etc., it appears to me that there is a 

 comparatively simple cause for this disappearance. George Henry 

 Lewes, Wilhelm Roux, and more recently Weismann, have all fallen 

 back on the assumed necessity of applying the principle of selection to 

 the several parts and specialisations of the individual organism, in 

 addition to the action of selection on the whole organism. The last 

 writer in particular, in his " Germinal Selection," suggests that a 

 struggle among the different parts of the germ-plasm may account 

 for the complete disappearance of rudiments, this germinal selection 

 thus supplementing the action of panmixia, personal or organismal 

 selection, etc. Now the necessity for increased co-ordination of 

 parts with increasing specialisation, entailing, as it necessarily must, 

 an increasing mutual dependence of each part on the others, must lead 

 as the type advances to diminished opportunity for any struggle of 

 parts in the organism, consequently if such a struggle exist at all it 

 must be limited to the most undifferentiated organisms. I do not 

 therefore see how this principle can explain the disappearance of rudi- 

 ments in any of the more specialised organisms, hence it does not seem 

 to be sufficient answer to the above-mentioned difficulty. In the 

 development of the individual we see a disappearance of structures, 

 which appear to become with advancing development useless, almost 

 parallel to the gradual disappearance of rudiments, etc., in the history 

 of the species evolution. And a common explanation for both of these 

 series of phenomena can, I believe, be satisfactorily found in the known 

 facts of nutrition. Growth of any tissue would seem to depend on 

 three conditions, a stimulus of the part adequate to promote func- 

 tional activity, a proper food supply, and efficient removal of products 

 produced by that particular tissue's activity. There is abundant 

 evidence to prove that a tissue tends to degenerate if its own excretory 

 products are not removed ; the evil effects produced by fatigue products 

 in muscle and other tissues on the activity of the tissue itself prove 

 that this factor must be of great importance wherever it is found to 

 occur. Just as the growth and development of bacteria is interfered 

 with, and finally altogether checked by the accumulation of products of 

 their own activity, so a tissue in the higher organisms has its activity 

 impaired and its power lessened when for some reason diminished 

 elimination of its own metabolic products occurs. Now both in the 

 development of the individual and the race we see an alteration of 

 structure, a gradual transition from the less to the more specialised, 



