316 



THE POPULAR SCIENCE MONTHLY 



of the body weight, and in hereditary cataract only about one twentieth 

 part of the lens becomes opaque, and yet this minute fraction of the 

 body weight shows the influence of heredity. Even the size, shape and 



Fig. 46. Diagram of Eight Different Races of Paramecium, Each Hori- 

 zontal Row (A-H) Representing a Single Race. The individual showing the mean 

 size in each race is indicated by + ; the mean of all the races is shown by the line 

 X-X. The numbers are the length in microns (one thousandth of a millimeter), x 43. 

 (After Jennings.) 



number of the cells in certain organs, and in given embryonic stages, 

 may be repeated generation after generation; and if our analysis were 

 sufficiently complete we should doubtless find that even the minute 

 parts of cells, such as nuclei, chromosomes and centrosomes, show in- 

 dividual peculiarities which are inherited. 



(b) Teratological and Pathological Peculiarities are really only un- 

 usual or abnormal anatomical characters, but of such interest and im- 

 portance as to deserve special mention. Many such abnormalities are 

 "undoubtedly inherited, among which are the following: polydactylism, 

 in which more than the normal number of digits are present ; syndactyl- 

 ism, or a condition of webbed fingers and toes; brachydactylism, in 

 which the fingers are short and stumpy and usually contain less than 

 the normal number of joints; acondroplasy, or short and crooked limbs, 

 such as occur in certain breeds of dogs and sheep and in certain hu- 



