PHENOMENA OF INHERITANCE 199 



lens of the human eye weighs only about 175 

 milligrams, or about one three-millionth part 

 of the body weight, and in hereditary cataract 

 only about one twentieth part of the lens be- 

 comes opaque, and yet this minute fraction of 

 the body weight shows the influence of hered- 

 ity. Even the size, shape and number of the 

 cells in certain organs, and in given embry- 

 onic stages, may be repeated generation after 

 generation; and if our analysis were suffi- 

 ciently complete we should doubtless find that 

 even the minute parts of cells, such as nuclei, 

 chromosomes and centrosomes, show individ- 

 ual peculiarities which are inherited. 



(b) Teratological and Pathological Peculi- 

 arities are really only unusual or abnormal an- 

 atomical characters, but of such interest and 

 importance as to deserve special mention, 

 Many such abnormalities are undoubtedly in- 

 herited, among which are the following: poly- 

 dactylism, in which more than the normal 

 number of digits are present; syndactylism. 

 or a condition of webbed fingers and toes; 

 brachydactylism, in which the fingers are short 

 and stumpy and usually contain less than the 



