400 



THE AMERICAN NATURALIST [Vol. L 



We shall be able presently to note more closely the con- 

 clusive facts as to the matter of a differential matura- 

 tion. Continuing our examination of the further data 

 which we know correlate with this sort of a sex-series we 

 shall meet with additional and other kinds of facts which 

 lead toward a constructive view of the nature and basis 

 of sex ; facts immediate and specific concerning the meas- 

 ured powers or capacities of these series of ova which 

 present us the sort of sex-series in question— facts which 

 reveal sex in quantitative terms. 



Correlations marked (2) and (3) on Chart 1 were first 

 noted by Professor Whitman. I have been able every 

 year to find many confirmations of his conclusions. 



The curve for "Developmental Energy" on the chart 

 indicates a progressive seasonal decrease of this capacity 

 in the fertilized eggs; a decrease from spring to autumn. 

 Now the evidence is unquestionable for the lowest part 

 of the curve —the autumn. In general, least develop- 

 ment proceeds from the last eggs of the season. These 

 are the largest eggs of the year. There is also less de- 

 velopment in the second eggs of the clutch. These are 

 the larger of the clutch. It is thus seen fhat the larger 

 the yolks the less "developmental energy" possessed by 

 them. 



The "Length of Life" of the several offspring of such 

 a sex-series tells again of an advantage possessed by the 

 earlier hatched birds, and of a more limited life-term 

 affixed to the later hatches. It is further probable that 

 within the group of clutches giving rise to females only, 

 a longer average life-term falls to those who hatched 

 from the first egg of the clutch, than to those arising 

 from the second. Here, then, as in correlation no. (2) 

 the smaller eggs of clutch and season are the eggs pro- 

 indicate that the basis of sex is a fluid, reversible process; that the basis 



(c) Bulletin of the American Aa.h m.u <>f ;>/.„' , •, , Vol. 15. No. 5 (Oc- 

 tober, 1914) (pp. 265-285), "The Determination of Sex and Its Experi- 

 mental Control. " "The sum of these results, together with the initial fact 



versible process, that the basis of adult sexual difference is a , v ,nntit,if<vt 

 rather than a qualitative thing (p. 277)," etc. etc. 



