BIOLOGY 



into the nature of the mechanism whereby in- 

 dividual peculiarities are handed on from parent 

 to offspring, and Cytology has thus become a 

 necessary adjunct to the study of Heredity. In 

 this connection we cannot but be struck with the 

 fineness of the texture of the living organism. So 

 fine is it that our most powerful microscopes and 

 most accurate methods of micro-chemical analysis 

 are inadequate to reveal the presence of organic 

 entities whose existence is fully established by 

 indirect methods. I may refer more particu- 

 larly to the so-called Mendelian factors, whose 

 material existence in the chromosomes of the 

 nucleus has recently been so ably demonstrated by 

 Professor Morgan and his colleagues in America. 

 These invisible structural units may perhaps be 

 almost of the same order of magnitude as the 

 molecules of the physicist, and their investigation 

 brings us very near to the border-line between 

 the biological and physical sciences. It is in 

 this direction, I believe, that some of the most 

 important and far-reaching developments of 

 Biology are to be expected in the near future, 

 but in saying so much I fear that I have already 

 encroached upon the domain of another depart- 

 ment of our subject, that of Biochemistry and 

 Biophysics. 



The study of Embryology, or form in the 

 making, which deals with the development of the 



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