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INTRODUCTION IT IS well established that the external environment influences sexual maturity in birds. Light is the most important environmental factor as shown by the work of Rowan (1925) with juncos (Junco hyemalis), Bissonnette (1930) with starlings (Sturnus vulgaris), Scott and Payne (1937) with turkeys. Experiments at the Nebraska station reported in 1930 had demonstrated that lighted turkeys could be induced to start laying earlier than those not subjected to artificial light, and this was confirmed by Albright and Thompson (1933) and the later work of Scott and Payne (1937). The hypophysis has been shown by Hill and Parkes (1937) to control gonad activity in birds. Benoit (1935) has obtained evidence that light acts on receptive organs which transmit stimuli to the hypophysis which in turn produces hormones that act on the gonads. Presumably there are inherited differences in the response of different individuals to a given length of day . . .

LERNER (1950) drew attention to the need for detailed information in poultry research about non-linear interactions between genotypes and environments and the extent to which they may affect breeding programs. No interaction between strain and ration was found for weights of turkeys by Asmundson and Lerner (1940). Since then, additional results have been accumulating which indicate that, under average conditions, this phenomenon may occur for some traits but not for others, thus leaving in some doubt the practical importance of these interactions in many economic traits in poultry. For example, Gowe and Wakely (1954) found no strain-environment interaction in the egg production of several strains of White Leghorns at 6 different Dominion Experimental Stations across Canada. Johnson and Gowe (1956) reported that, in a similar test for egg quality, involving 8 White Leghorn strains, there was no interaction in the the case of albumen quality and shell strength, although a . . .

Statistical analysis of the trapnest records of turkeys extending over seven years shows that date of first egg is a better measure of sexual maturity in turkeys than age at first egg. Date of first egg is little influenced by variation in the time of hatch within the normal hatching season of almost two months, whereas age at first egg is influenced, the later-hatched birds starting to lay when younger than the earlier-hatched birds. Moreover, genetic differences in sexual maturity can more readily be demonstrated with date of first egg than with age at first egg. Selection for early and late sexual maturity was effective in establishing lines that differed significantly in date of first egg. When these lines were crossed the results differed according to which way the cross was made. The progeny of late male x early female laid earlier than the birds in the late-maturing line but later than the progeny of the reciprocal cross. In at least one case, the progeny of the latter (early male x late female) la...

A mosaic occurred in theF 2 generation of a cross of a Bronze male on a Bourbon Red female. This bird was bronze on the head, neck, shoulders, tail and part of the rump with some patches of bronze feathers surrounded by red on the wings. The rest of the bird was covered with feathers typical of the Bourbon Red variety which thus formed a continuous band around the middle of the body. The difference in the plumage colour of the two varieties was found to depend upon a single pair of autosomal genes, the ratio in theF 2 generation being approximately 1 Bronze to 2F 1 pattern to 1 Bourbon Red. The hybrids resembled the Bronze variety more than the Bourbon Red, particularly in down pattern and adult plumage, but were readily distinguished from both parental varieties. The possible mechanisms that may account for this case are discussed.

THE consequences of one or more of a large number of isolating mechanisms are that birds of different species or genera either do not mate or mate only rarely (Dobzhansky, 1951; Riley, 1952; and others). Ecological isolation kept apart the three genera with which we are here concerned for a long time before they were brought together by man. Even then, sexual or psychological isolation has reduced or prevented mating between them. Only between the chicken (Gallus) and ring-necked pheasant (Phasianus colchicus) have many natural hybrids been recorded (Suchetet, 1896; Wheeler, 1910; Poll, 1912; Cutler, 1918; Serebrovsky, 1929; Yamashina, 1942). Turkeys (Meleagris gallopavo) are placed in a different family from pheasants and chickens (Friedmann, 1946) and are much larger birds. Despite the additional barrier of size, one natural hybrid of the turkey and pheasant has been reported (Edwards, 1761) but none between the turkey and chicken. The isolating mechanisms may . . .

IN studies of inheritance of rate of growth in the domestic fowl by Lerner and Asmundson (1932) and Asmundson and Lerner (1933), a modified formula of Minot measuring the rate of growth was used on data for certain periods of growth (3-12 weeks of age and 8-12 weeks in studies on Ancona × Light Sussex crosses, and 2-8 weeks of age on Leghorns). The choice of the particular formula for the average rate of growth, (1) R = W 2 - W 1 1 / 2 ( W 2 + W 1 ) 100 was based largely on simplicity of operation. No claim was made as to the accuracy of the formula as a measure of rate of growth, but since only comparative figures were required the formula was considered satisfactory. With regard to the choice of periods suitable for such study, however, a number of factors had to be considered. Aside from the desirability of a short period, in order to avoid carrying a large number of . . .

THE long axis of the avian embryo in the normal hatching position coincides with that of the egg, the beak being under the right wing with the tip of the beak towards the air cell in the large or blunt end. Sanctuary (1925) pointed out that many embryos that fail to hatch are not in the normal hatching position and that this may be a factor in their failure to hatch. He reported the frequency of three malpositions, one of which had been observed by Reamur in 1751 (Hutt and Pilkey, 1934). Further observations have since been reported by Hutt (1929), Smith (1930), Hutt and Cavers (1931), and others. The causes that determine the final position of the embryo in the egg have been investigated. Taylor (1932) found that a larger proportion of the malposition head in small end of egg occurred when the 6-day-old embryos were improperly oriented, than . . .