772 EXPERIMENT STATION RECORD. [Vol. 37 



It has been further shown that the expression of spangling may be greatly 

 modified, or even entirely obscured, by the action of other factors, especially 

 factors for black pigmentation, which, however, segregate independently of the 

 factor for spangling. The independence of the spangling factor is indicated by the 

 fact that, after segregation and recombination of the several factors concerned, 

 some individuals are extracted in which all disturbing factors are absent and 

 the spangled pattern is exhibited In its original purity. A number of such 

 birds have been obtained from different matings. and these now breed as true 

 to spangling as do the Silver Spangled Hamburgs themselves. 



Mendelian inheritance in poultry, G. Levevke {Abs. in Missouri Sta. Bui. 

 i47 (1917). pp. Jfl, 48).— This is another abstract of the data reported above. 



The structure of the fowl, O. C. Bradlkt {London: A. d C. Black, Ltd., 1915, 

 pp. XII +153, pis. n, figs. 2S). — A concise descriptive anatomy of the fowl, with 

 a chapter on the embryology of the chick. 



Studies on the physiology of reproduction in birds, I-VII, O. Riddle et ax. 

 (Amer. Jour. Physiol. 41 (1916), No. 5, pp. SS7-431 ; ^S (1916), No. 1, pp. 151- 

 162). — In this series of articles, the first seven of which are here noted, results 

 ar« given of studies of the physiology' of avian reproduction in relation to the 

 problem of heredity and sex. 



I. The occurrence and measurement of a sudden change in the rate of gro^cth 

 of avian ova, O. Riddle. — Continuing studies already noted (E. S. R., 26, p. 164), 

 it has been shown that when the oocyte of the fowl reaches a diameter of about 

 6 mm. it increases its previous rate of growth to a rate nearly 25.8 times higher. 

 The transition from the one rate to the other is made in a single day and sharply 

 marks off the type of substance accumulated in the ovum. Under the slower 

 rate this is white yolk. Under the greatly increased rate the yellow yolk is 

 produced. The increased rate of deposition of yolk materials is accompanleil by 

 a pronounced alteration in the growth and activity of the membrane (follicular) 

 which surrounds the ovum. A comparable change in growth rate occurs gen- 

 erally in other avian and sauropsidan eggs. 



II. On the chemical compo'iition of ichite and yellow egg yolk of the fowl 

 and pigeon, Adelaide A. Spohn and O. Riddle. — By taking advantage of the 

 fact that the ova of the fowl consist wholly of white yolk until they begin their 

 final period of rapid development (see above) the authors were able to prepare 

 samples of tht two kinds of yolks for analysis. The results of the analyses of 

 two samples of white yolk and of six samples of yellow yolk of the common 

 fowl demonstrate that the two forms of yolk are strikingly different substances, 

 and that the white yolk much the more nearly approximates the composition of 

 small holoblastic eggs, and of living undifferontiatetl tissue generally. The 

 ovarian egg (yellow yolk) of the fowi contains little more than 45 per cent of 

 water. The solids of the fowl's egg contain 20.6 per cent of phosphatids, 49.5 

 per cent neutral fat, and 28.4 per cent protein. 



Analyses were also made of two samples of yellow yolk of the jungle fowl 

 and five samples of yellow yolk of the common pigeon. The results indicate 

 that the yellow yolk of the Jungle fowl has probably a lower lipoid and a higher 

 protein content than the yolk of domestic fowls. The yellow yolk of the pigeon 

 differs most from that of the fowl in it.s much higher moisture value, but prob- 

 ably differences in the amount of alcohol-soluble and protein materials also 

 exist. The yellow yolk derived from different orders, genera, and species of 

 birds probably varies more in the amount of water than in other fractions, but 

 the yellow yolk from birds of different orders is relatively much alike a.s com- 

 pared with yellow and white yolk from the same Individual bird. 



III. On the metabolism of the egg yolk of the fowl during incubation, O. 

 Riddle. — In this study on the changes in the egg yolk during incubation the 



