32 Zoologia: N. Y. Zoological Society. [Vol. I 



Perhaps the most interesting part of Prof. Whitman's 

 paper is that relating to eight years' experimental breeding of 

 domestic pigeons. In the offspring of checkered birds, by careful 

 selection, birds with fewer checkers were produced, these check- 

 ers gradually merging into three and two bars, and at last into 

 one, following which came total obliteration of dark color on the 

 wings. It was found impossible to reverse the process, that is, 

 to obtain doves of the checkered type from typically barred birds. 

 Hence the author assumes that "the direction of evolution can 

 never be reversed." 



In comparing these statements with the results which I have 

 obtained with doves under the influence of humidity, there is one 

 fact of which we must never lose sight — perhaps the most im- 

 portant factor with which we shall have to deal, when future 

 experiment enables us to stand on firmer ground. This is, 

 whether we are dealing with acquired or with congenital charac- 

 ters. In the case of the individual Scardafella doves there is 

 certainty that the seeming atavistic characters are acquired. 



Nine genera of Columbi formes are found in the United 

 States, one of which, Ectopistes — the passenger pigeon — is au- 

 tochthonous, at least in its present distribution, while Zenaidura 

 — the mourning dove — extends southward only as far as Pan- 

 ama. The remaining seven are highly developed in the Neo- 

 tropical Region, hence we may be reasonably certain that the 

 Columbine element in the North American fauna is of tropical 

 origin. 



This would indicate that those forms of doves and pigeons 

 which barely extend over our southern border have been derived, 

 more or less recently, from tropical types. Accepting this as a 

 fact, then in reproducing a tropical atmospheric environment 

 for our Scardafella inca and by this means rehabilitating it in 

 its ancestral plumage, we apparently demonstrate an exception 

 to the assertion of Prof. Whitman that "the direction of evolu- 

 tion can never be reversed." 



On the other hand, the modus operandi of this atavistic 

 change seems to support that author's orthogenetic theory, in 

 so far as the recapitulation follows along the same lines (1) 

 as in related genera of doves, and (2) in the identity of the de- 

 tails of the change in several individuals. This indicates that 

 this humidity-induced variation is neither fortuitous nor direc- 

 tionless. 



Interesting and significant as the results are, they but open 

 up innumerable new vistas of unexplored fields. If the melanic 

 doves were bred, would there be any trace of inheritance of these 



