1899] THE SCOPE OF NATURAL SELECTION 129 



and in this gradual transition there must be, as I endeavoured to 

 prove in niy answer to the last objection, an alteration in the line of 

 functional activity of the parts, and that, owing to this fact, a tissue 

 that was necessary in the earlier stages, became less and less so as 

 specialisation advanced, the whole tendency of the specialising organism 

 being continually and increasingly against the earlier, less specialised, 

 stages. It will thus happen that every structure which is becoming- 

 useless owing to its deficient specialisation, whether in the history of 

 the race or the individual, will have two adverse sets of conditions to 

 contend with — one defective elimination of its own tissue products, 

 owing to its becoming increasingly removed from the growing organismal 

 specialisation of food products, while secondly, for this same reason, 

 its own food supply will become less and less suitable.- This theory 

 would apply equally to germinal and somatic development and atrophy 

 of structure ; there would thus, through the alteration of functional 

 activity of the whole organism, be brought about elimination of all 

 structures not in the line of evolution, and therefore organismal 

 selection alone, if this theory is sound, would be able to explain the 

 complete disappearance of rudiments, the various forms of develop- 

 ment and atrophy, without calling to its aid climatic inheritance, 

 panmixia, and germinal or any other form of particular selection. 



The only two other important objections against the principle of 

 selection are (1) those cases where it is assumed that automatism 

 produced by habit has become hereditary (instinctive), 1 an assumption 

 which an examination of the facts does not appear to warrant, and 

 (2), those cases which are supposed to be examples of experimental 

 demonstration of acquired inheritance. 



In the best known of these experiments, particularly those per- 

 formed by Brown-Sequard, we have certain facts which appear to show 

 that under very exceptional conditions somatic injuries may affect 

 germinal structures. Assuming that reliance may be placed on this 

 interpretation of these experiments, an interpretation which future 

 facts might conceivably negative, there are other facts associated with 

 the relation of environment, alcohol, etc., to crime and insanity which 

 would seem to offer some slight confirmation of this view. If further 

 investigation proved the possibility of somatic responses affecting 

 occasionally the germinal structures, it would only affect any theory of 

 heredity which was based on the assumption that somatic and ger- 

 minal elements were completely isolated. The purely selectionist 

 position would remain intact unless direct climatic accommodation could 

 be also proved to be a factor of importance. The objections to the 

 selectionist theory do not appear, therefore, when examined, to be valid. 



1 See Lloyd Morgan's "Comparative Psychology" and "Habit and Instinct," and 

 Mr. E. L. Thorndike's experiments. 



{To he continued.) 



9 NAT. SC. VOL. XV. NO. 90. 



