382 



THE AMERICAN NATURALIST 



[Vol. LIU 



mean egg- weight begins to rise again and reaches a sec- 

 ond mode or maximum in September, at which peak the 

 mean egg weight is slightly higher than for the period of 

 the vernal maximum (April). This September peak may 

 be called the autumnal weight maximum. The mean dif- 

 ference between the vernal maximum and the autumnal 

 maximum is usually about one or two grams. Having 

 attained this peak of weight, the curve drops again 

 through October to strike its fundus in November (the 

 first month of the second laying-year).^ From this point 

 it rises in December to the first weight maximum 

 {hibernal weight maximum) of the second laying year, 

 and then drops again in January to form the hibernal 

 weight minimum immediately preceding the vernal max- 

 imum of the second year. 



It will now be clear to the reader that there exists a 

 noteworthy circumstance with reference to these curves 

 of numerical production and of egg-weight : they parallel 

 one another to a remarkable degree. The vernal maxima 

 of production and of weight fall together in April; and 

 the autumnal maxima of production and of weight fall 

 together in September. The only d.^parture from coin- 

 cidence lies in the circumstance that the summer produc- 

 tion minimum arrives in An,i;ust, wliih' the summer 

 weight minimum is found in July. It should be said, 

 however, that the plotting of the curves on ten or five-day 

 ordinates might show a closer correspondence of these 

 minima in point of time. The difference observed is 

 scarcely significant. The definite agreements in the 

 trends of the respective curves are taken to indicate that, 

 on the average, increased production is accompanied by 

 ineroasod mean wei.ii'lit of the eggs produced; and that, 

 r;-rr i-rrsa. a decivase in ])r()(hu'tion is, on the average, 

 aceonqianied hv (h'civas.Ml mean wei-lii in the eggs pro- 

 duced. \Vhatever, therefore, umv he the ])iological sig- 

 nificance of the two pro.hiction maxima for the hen's first 



Bit has become common to consi,l, r tlx' laying year of a hen as extending 

 from November 1 of the jaillet year t.> ami iiichuling October 31 of the year 

 following. 



