384 



SCIENCE 



[N. S., Vol. XL., No. 1028 



of long or short period) in the egg production 

 of a single individual bird, owing to the fact 

 that the production is in discrete units. 

 Yet while the end products of ovarian 

 activity are discrete units there are very 

 strong reasons for supposing that physio- 

 logically the elaboration — or production in the 

 broad sense — of eggs by the ovary is a con- 

 tinuous process. This matter has been rather 

 fully discussed in a former paper from this 

 laboratory.^ Evidence of another sort for the 

 continuity (in the mathematical sense) of 

 ovarian activity has recently been given by 

 Gerhartz* in a valuable paper on metabolism 

 in the fowl. 



2. By a simple statistical expedient it is pos- 

 sible to represent the changes in rate of 

 fecundity in an individual bird as a continu- 

 ous curve, of which the ordinates represent the 

 rates of egg production on a percentage scale 

 (0 to 100) at the time intervals plotted as 

 abscissse. This is done by taking, as the rate 

 of fecundity for any given day Pn, the per- 

 centage which the actual number of eggs laid 

 by the bird during the 21 days of which j9„ is 

 the central day, is of 21. Put as a formula, if 



Bpn = rate of fecundity (or ovarian activity 

 as indicated by ovulation) on the 

 day Pn, 

 1 ^ an egg produced, 

 and 5 denotes summation between the indi- 

 cated limits, we have 



ioo(S?:!;:i) 



it^„ = ■ 



21 



The rates so calculated for each successive 

 day may be plotted as a curve. 



3. The reasons why 21 days are chosen as 

 the basis of the calculation rather than some 

 other odd number of days will be fully dis- 

 cussed in the complete paper. Here it need 

 only be said that there are good biological 

 grounds for this choice. Gerhartz^ has 

 shovra, for example, that this number repre- 



s Cf. Pearl and Surface, loo. cit. 



•* Gerhartz, H., ' ' Ueber die zum Auf bau der 

 Eizelle Botwendige Energie (Transformationsen,- 

 ergie)," Pflii-ger's Arch., Bd. 156, pp. 1-224:, 

 1914. 



5 Loc. oit. 



sents about the average number of oocytes to 

 which any appreciable addition of yolk is 

 being made at any given instant of time. 



4. Applying this method to records of one, 

 two and three year old hens many interesting 

 and novel points regarding ovarian activity, 

 as expressed in ovulation, may be made out. 

 The long period secular cycles of production 

 appear much more clearly and precisely than 

 in flock mass statistics. The steady diminu- 

 tion in maximum rate of fecundity per unit 

 of time after the first spring cycle in the bird's 

 life is very strikingly shown in the great 

 majority of eases. 



This method of measuring fecundity opens 

 the way to the attacking in the individual of 

 a number of problems which hitherto have only 

 been amenable to indirect, statistical treat- 

 ment. Such, for example, are the questions 

 of relation of size of egg to rate of fecundity, 

 the relation between fertility (in the fowl 

 readily measured by hatching quality of eggs) 

 and fecundity. There are many other inter- 

 esting biological problems relating to repro- 

 duction in birds, the analysis of which will 

 certainly be aided by the method here discussed. 



The complete paper describing the method 

 and illustrating it fully by examples will 

 shortly be published elsewhere. 



Eaymond Pearl 



THE NOBTE CAROLINA ACADEMY OF 

 SCIENCE 



The North Carolina Academy of Science met in 

 its thirteenth annual session at Trinity College, 

 Durham, on Friday and Saturday, May 1 and 2, 

 1914, with 28 members in attendance. The execu- 

 tive committee held a meeting in the early after- 

 noon of Friday, and this was followed by a gen- 

 eral meeting for the reading of papers. At night, 

 after Dean W. I. Cranford had welcomed the 

 academy to Trinity College, President Franklin 

 Sherman, Jr., of the academy, read his presiden- 

 tial address, "The Animal Life of North Carolina 

 with some Suggestion for a Biological Survey." 

 Following this, Professor A. H. Patterson gave a 

 lecture on "The Gyroscope and its Modern Appli- 

 cations" with demonstrations of some fine appa- 

 ratus. Next Mr. Bert Cunningham gave a strik- 

 ing demonstration of the new nitrogen tungsten 

 lamp, comparing its light efS.eiency with that of 



