No. 596] EVOLUTIONARY THEORY 457 



Comparative Table 





g f 



1 



i 



1 



1 



IS 



IP 



1 



1. Proopic brachycephaly, abbrevia- 

























2. Sudden development of horns on 



















•• 







y 



I 



X 











4. Jaw appendages 



5. Taillessness, absence of eaudals. . . 



6. Short-leggedness, or limb abbrevia- 



x 



X 



* 













7. ConsoHdation of paired'hoofs; syn- 











8. Polydactvlism 





10. Mottled skin markings 



11. Excessive hairiness, or length of 



12. Hairlessness, entire absence of 



















13. Ex.-essivdv fine or silky hair 



14. Kaverse.1 hairs 









15. Curled-hair. 



















the cat, the dog, the goat, the sheep (Lincoln) and others. 

 So in different species of Drosophila, I am informed by 

 Dr. C. W. Metz, the same mutations occur— of course, 

 without any relation to environment. 



In a strain that has produced a mutation once we are 

 apt to find the same mutation a second time. Thus De 

 Vries states that the peloric toadflax does not set seed in 

 nature, yet it occurs repeatedly in a given locality and 

 even in distant localities. We conclude there is some- 

 thing in the structure of the germ plasm of the toadflax 

 that permits a wholly useless, and indeed not naturally 

 perpetuated, mutation to occur easily. Similarly, doub- 

 ling of the floral parts occurs again and again in wholly 

 unrelated species ; often combined with complete sterility. 

 Again, poultry sometimes show a great extension of the 

 web between the toes. This occurs chiefly between digits 

 III and IV, exactly where the syndactyl web occurs in 

 man and where it occurs in wading birds that have only 

 a single web between the toes- of which 8 genera might 



