90 Vererbung, Variation, Mutation. 



218) Pearl, B. and McPheters, L. M., A Note on Certain Biometrical Compu- 

 tations. In: Amer. Nat. Vol. XLV, S. 756—760, 1911. 



Gives a table of the sums of the logarithms of the natural numbers from 1 to 100, 

 «nd certain related functions. Pearl (Orono). 



219) Pearl, R., Biometrie Ideas and Methods in Biology. Their Signi- 

 ficance and Limitations. In: Scientia, Vol.X,(XIX— 3) 1911, S. 101— 119. 



A discussion of the development of biometry and its relation to biology. 

 It is pointed out tliat biometric methods are purely descriptive in their nature 

 and subject to the limitations thereby implied. These methods do, howewer, 

 make possible the description of groups (varieties, species, etc.) as such, rather 

 than in terms of individuals. The probable error concept in a farther valuable 

 contribution of biometric work is emphasized, and the weakness in this respect 

 of the biometric method of attacking the problem of inheritance is discussed. 



Pearl (Orono). 



^20) Pearl, ß. and Bartlett, J. M., The Mendelian Inheritance of 

 Certain Chemical Characters in Maize. In: Zeitschr. indukt. Abst.- und 

 Vererb.-Lehre. ßd. VI, S. 1—28, 1911. 



In a cross between white sweet (cT) and yellow starchy ($) races of maize 

 it was shown that (l) moisture, (2) nitrogen and protein, (3) crude fat (ether 

 ■extract), (4) ash, (5) crude fiber, (6) pentosans, (7) sucrose, (8) dextrose (9) total 

 sugar, and (ll) starch behaved in the F^ and F^ progeny as though they were 

 definite unit characters inherited in Mendelian fashion. "High content" and "low 

 content" in respect to these characters definitely segregated. Pearl (Orono). 



221) Pearl, Raymond, Some recent studies on Variation and correlation in 

 agricultural plants. In: Amer. naturalist, 45, S. 415 — 425, 1911. 



A review of a number of papers, showing the gradual increase in the use of bio- 

 metrical methods in the study of variability and correlation of characters in agricul- 

 tural plants. Gates (London). 



222) Pearl, R., Breeding Poultry for Egg Production. In: Ann. Rpt. 

 Me. Agr. Ep. Sta. for 1911, S. 113—176, 1911. 



This paper summarizes investigations on the problem of the inheritance of 

 fecundity in the domestic fowl which liave extended over 13 years. The most 

 important results were the following: 



An experiment in which the higliest laying liens were used as breeders showed 

 that mass selection for high egg production on the basis of the trap nest record 

 of the individual alone did not, as a matter of fact, result in a steady continuous 

 improvement in average flock production, even though it was continued for a 

 period of ten years. A further experiment along the same line showed that 

 the daughters of "200-egg" hens with from six to nine years selected ancestry 

 (on the basis of trap nest records) behind them were no better layers, on the 

 average, than birds bred from the general flock. There is no evidence that 

 either (a) the method of housing, or (b) of feeding, or (c) the fact that the 

 chicks were throughout the period of the experiment hatched in incubators and 

 reared in brooders, or (d) the fact that some degree of Inbreeding was practiced 

 during the mass selection experiment had anything whatever to do with the 

 outcome of that experiment. It is specifically shown that during the period of 

 selection the adult mortality decreased. It is further shown that at the present 

 time, in spite of the fact that there has been no change in the method of hatching 

 and rearing by artificial means, the records of hatching and of chick mortality 

 are such as to give no indication whatever that the strain of Barred Plymouth 



