Aves. 43 



Akademie der Wissenschaften. — St. Petergburj^er Universität. — Kasaner Universität. 

 — Tomsker Universität. — Polytechnisches Institut zu Kiew. — Charkower Veterinär- 

 institut. — (Kurze Übersichten über die in diesen Instituten geleisteten ornithologischen 

 wissenschaftlichen Arbeiten.) — Personalia. Varia. C. Greve (Kiga). 



90) Pearl, R. and F. M. Surface, A biometrical study of egg produc- 

 tion in the domestic fowl. II. Seasonal distribution of egg produc- 

 tion. In: Bull. 110, part II, Bureau of Animal Industiy, U. S. Dept. Agr. 

 S. 81—170, 1911. 



The first part of this paper dealt with tlie total annual egg production, 

 while the distribution of egg production during the months of the year is con- 

 sidered in the present paper, which gives an elaborate mathematical analysis of 

 data extending over several years. The "laying year" is divided into four natural 

 periods: (l) November to March, the winter period, in which egg-laying is essen- 

 tially a non-natural, stimulated process; (2) March to June, the spring period, 

 the natural laying period of the wild Gnlliis; (3) June to September, the 

 Summer season; and (4) September and October, the moulting period. The lowest 

 mean production in November is followed b}' a rapid increase in December and in 

 January, the maximum being reached in March. After April there is a steady 

 decline until October. The greatest variability in egg production is in November, 

 at the beginning of the laying year. The lowest variability is in April. Eight 

 y^ears breeding selection produced no increase in the mean egg production of 

 any month in the year, the mean production in all but two of the months sliow- 

 ing on actual decrease. 



It is found that keeping the birds in larger flocks distinctly lowers the 

 Summer egg production, but has no effect on the winter production. 



The term "antimode" is used to designate "the point in äny bimodal fre- 

 quency distribution where the frequency over a unit base dement is at a mi- 

 nimum". 



The frequency distribution for each month of the year gives a bimodal 

 S-shaped curve, although the material may be regarded as homogeneous. This is 

 explained by the hypothesis (which is shown to fit the facts) that egg-laying 

 in each bird occurs in defiuite cycles which alternate with nonproductive periods, 

 the bimodal curve for each month being the sum of two unimodal skew fre- 

 quency curves, Gates (London). 



97) Pearl, B. and Curtis, M. ß., Studies on the Physiology of Re- 

 production in the Domestic Fowl V. Data Regarding the Physiology 

 of the Oviduct. In: Journ. Exp. Zool. Vol. 12, S. 99—132, 1912. 



Quantitative and chemical data are presented regarding the secretion of 

 albumen in different regions of the oviduct. The sequence of events in the lor- 

 mation of the egg envelopes is shown to be as follows: 



After entering the infundibulum the yolk remains in the so-called albumen 

 portion of the oviduct about three hours and in this time acquires only about 

 40 to 50 percent by weight of its total albumen and not all of it as 

 has hitherto been supposed. During its sojourn in the albumen portion of 

 the duct the egg acquires its chalazae and chalaziferous layer, the dense albumen 

 layer, and (if such a layer exists as a distinct entity, about which there is some 

 doubt) the inner fluid layer of albumen. Upon entering the isthmus, in passing 

 through which portion of the duct something under an hour's time is occupied 

 instead of three hours as has been previously maintained, the egg receives its 

 Shell membranes by a process of discrete deposition. 



