1 88 / LIONEL TAYLER [September 



is due to a structural difference existing in the protoplasm itself, that 

 the assimilative power of an organism depends not on its environment 

 but upon its structure, and that these structural peculiarities are never 

 modifiable, although they may be adapted through elimination of 

 unfit and less fit, and subsequent reproduction among the surviving 

 favoured organisms, and repetition of this process until a better and 

 better adapted organism is produced, we have an explanation which 

 satisfactorily accounts for both the constancy and the variability of 

 the many forms of plant life. 



Again, the constancy of all low forms of life under varying 

 conditions is often remarkable. In view of the fact that these 

 unicellular organisms are not easy to keep under constant observa- 

 tion, that their reproductive power is often enormous, and that it 

 is at present very difficult if not impossible to place them under 

 test conditions to prove whether or no they are capable of being 

 directly modified by changes in temperature, food, etc., it is worthy of 

 note that the few recorded experiments have taken years and not 

 months or weeks to induce any change in the organism, and this 

 suggests elimination rather than direct modification as the main if not 

 sole agent. 



The science of bacteriology is surely strong presumptive evidence 

 that no very rapid modification of form and habits is affected by 

 altered conditions in these low forms of life ; the constancy of the 

 characters of diseases known to be produced by these forms of micro- 

 organisms, and the fact that the bacteriologist can frequently tell by 

 the form and behaviour of the bacillus, micrococcus, etc., what disease 

 it will induce, and this in spite of the immense capabilities for 

 modification under changed conditions, etc., that its habits afford, 

 are all arguments against direct climatic accommodation. 



Another point which appears to me to throw very considerable 

 light on the subject is the behaviour that all organisms, as far as 

 I know, without exception, exhibit towards their environment. 

 Local conditions of light, heat, food-supply, do not appear to modify 

 organisms in a certain definite manner as one would expect were 

 direct climatic accommodation possible ; on the contrary, the action of 

 every organism to its environment, from the lowest to the highest, 

 appears to be selective, the response of certain internal activities to 

 outside conditions. Kecent observations made on the phagocytes of 

 the blood show that the determination of their movements is partly 

 chemical, that they move away from some and towards other products ; 

 their action is selective. Plants living on the same soil do not make 

 use of the same material, and it is perfectly extraordinary what 

 minute quantities of a substance can be utilized if it be needed by the 

 organism. Iodine and its selection from sea-water by some forms 

 of sea-weed is a case in point. Precisely similar results occur in the 

 animal kingdom. The same choice of food is manifested in different 



