THE INTRODUCED SPARROW. 1 3 



ing factor, and it is perfectly natural that certain less plastic 

 individuals should, through the influence of heredity, continue 

 loyal to the British standard; for the tendencies toward the 

 establishment of a new type are not the result of the selection 

 of the fit nor the elimination of the unfit, but, rather, the result 

 of a direct influence upon all. 



The questions remain to be answered: Are the new varia- 

 tions the result of the influence of the environment reiterated 

 in the case of each particular individual, or has the mechanism 

 of heredity been affected so that the American birds are 

 producing new eggs through its directive influence ? Has 

 " Buffon's factor " (Osborn, '94), the direct action of environ- 

 ment, produced definite and adaptive variations which are 

 merely " contemporary individual differences " (Cunningham, 

 '93), or are these variations approved and adopted as a part of 

 the constitution of a phyletic series ? In brief, is the new variety 

 merely ontogenic, or is it phylogenic ? 



The maturating as well as the developing ovum must be 

 looked upon as an organism, and "as such must dominate its 

 own development " (Whitman, '94). The ovarian ovum gathers 

 to and about itself certain constituent parts and incorporates 

 them according to its individual peculiarities. As it leaves the 

 ovary, laden with yolk, it gathers about itself the envelopes of 

 albumen, shell-membrane, and shell which it is the function of 

 the oviducal walls to secrete. To assume that the organized 

 ovum has no control, exercises no influence over the development 

 and arrangement of these secondary envelopes, is like assuming 

 that the presence of an ovum in the mammalian uterus exer- 

 cises no influence upon the uterine walls. But the material 

 submitted to the ovum by the somatic cells is not necessarily 

 always qualitatively and quantitatively the same, and, on the 

 other hand, there is no reason to suppose that any two ova, 

 even of the same parent, have precisely the same peculiarities. 

 The entire bird's ^gg is the result of the centrifugal influence 

 of the ovum exerted upon the surrounding tissue no less than 

 the centripetal influence of the surrounding tissues exerted 

 upon the ovum; of the keimplasm exerted upon the soma no 

 less than of the soma exerted upon the keimplasm, and, in 



