CHROMOSOMES IN MAM. 301 



families, and it is therefore likely that every one has some chro- 

 mosomes with a predisposition to some disease, such as phthisis, 

 or gout, or diabetes, or " nerves." A mosaic made up of con- 

 tributions from eight families can hardly avoid some such taint. 

 But the important point, Prof. Ziegler continues, is this, what 

 numerical proportion do the tainted chromosomes bear to the 

 untainted ? If 3 out of the 24 have a diabetic taint, this will 

 mean much less than if there were 12 tainted. It follows that 

 taint on both sides of the house is particularly dangerous. 

 Ziegler gives the following illustrative schema. 



Father with marked taint, inherited from his father 

 and mother, as shown by the dark chromo- 

 somes 13 out of 24. 



ooo oo ooo ooo ooo ooo ooo ooo 



Tiirec mature sperm-cells - OOO 



showing three different b. OOO OOO OOO OOO 



000 000 



Mother normal, though with a latent taint, inherited 

 f.om her mother, as shown by the dark 

 chromosomes 4 out of 24. 



OOO OOO OOO OOO OOO OOO OOO OOO 



Three mature eg.-cells f * O O O OOO OOO OOO 



showing three different \e. OOO OOO OOO OOO 



(/.OOO 000 000 000 



It is evident that the child resulting from a x d would have 

 a badly tainted inheritance, that another resulting from c x f 

 would have a good inheritance, and that another from c x e 

 would be in the same position as the mother, and so on. 



The practical importance of this very theoretical inquiry is 

 great, for we have here a suggestion of the way in which taints 

 may fall out of a lineage. A tainted determinant may be liter- 

 ally lost in the course of the reducing divisions of the germ-coll* 



