186 ORIGIN OF NON-SEXUAL CHARACTERS 



three wild species of duck, Anas boscas (the Mallard) 

 with Dafila acuta (the Pintail) and with Anas tristis. 

 In the former cross he states that except for one or 

 two characters there seemed to be no more tendency 

 to variation in the F 2 generation than hi the F r An 

 F l Pintail-Mallard ? was mated with a wild Pintail $. 

 According to Mendelian expectation the offspring of 

 this mating should have been half Pintail and half 

 Pintail-Mallard hybrids, but Phillips states that 

 on casual inspection the plumage of all the males 

 appeared pure Pintail although the shape was 

 distinctly Mallard-like. The statement is, however, 

 open to criticism. The question is, what were the 

 unit characters in the parent species ? If the unit 

 characters were very small and numerous, an in- 

 dividual in which all the characters of the Pintail 

 existed together among the offspring of the hybrid 

 mated with pure Pintail would be rare in proportion 

 to the individuals presenting other combinations. 

 Of the F% s obtained from crossing Anas tristis $ with 

 Anas boscas $, Phillips obtained 23 females and 

 16 males. The females were all alike and similar to 

 F! females. Of the males one was a variate specially 

 marked, about half-way between the F 1 type and 

 the Mallard parent. This, according to Phillips, was 

 a segregate. The rest showed a range of variation 

 but no distinct segregation. 



It is somewhat surprising that Mendelian experts, 

 who seem to believe that species are distinguished 

 by Mendelian characters, have not made systematic 

 experiments on the crossing of species in order to 

 prove or disprove their belief. 



For my own part I cannot help thinking that the 

 origin of varieties in species in a domesticated or 



