574 EXPEEIMENT STATION EECOED. 



feathers which developed immediately after the operation were like those of 

 the male, but those which developed still later were female. Many were partly 

 male and partly female, the male portion in some instances being separated 

 by a clear-cut transverse line from the female part. A regenerated ovary 

 has been found in all such instances. In birds which were molting when 

 completely ovariotomized the partly grown feathers exhibited the first sign 

 of male characters about ten days after the operation, so that it seems 

 probable that the change in the mode of development must take place almost 

 immediately. . . . 



" We may conclude, therefore, that while both the ovaries and testes pro- 

 duce internal secretions, their effect is quite difCerent, that of the ovary being 

 the most striking in that it is responsible for development of the female 

 secondary sexual characters. Possibly, as a working hypothesis for birds, we 

 may assume that the secondary sexual characters of the male, subject, of course, 

 to the above observations on the comb, wattles, and ci'owing instinct, are com- 

 mon to each sex, but are modified in the female, imder the influence of the 

 ovary, into her characters. Hence, after castration the male characters de- 

 velop while in the male no comparable change takes place." 



On the ryhthm of egg production, H. D. Good axe {Jour. Amer. Assoc. Instr. 

 and Invest. Poultry Ilust)., 1 {1915), No. 3, pp. 18, 19). — It has been observed 

 at the Massachusetts Experiment Station that most hens lay for a period of 

 several days and then skip one. The first day of a series the hen lays early 

 In the morning. The time she lays the next day depends largely on the char- 

 acter of her particular rhythm. If the rhythm is such that she lays only every 

 other day, she usually lays about the same time each day, i. e., 10 a. m., 0, 11 

 a. m., 0, 10 a. m., 0, 11 a. m. If she lays two days out of three, the first egg 

 is laid during the morning and the second during the afternoon, i. e., 10 a. m., 

 3 p. m., 0, 10 a. m., 2 p. m., 0, 9 a. m., 1 p. m., 5 p. m., 0. As the period lengthens 

 the number laid in the morning increases until the larger proportion are laid 

 before noon. Thus, 8 a. m., 9 a. m., 10 a. m., 10 a. m., 10 a. m., 10 a. m., 9 a. m., 

 10 a. m., 9 a. m., 5 p. m., 11 a. m., 11 a. m., 5 p. m., 11 a. m., 11 a. m., 2 p. m., 

 2 p. m., 4 p. m., 0. There is, however, much variation. 



Some hens lay every other day, or we may say, a ^ rhythm, others §, that is, 

 two days out of three, others f, and so on. None of these types are character- 

 istic of any one hen. Many individuals, however, seem to center about a 

 particular rhythm. 



On the basis of winter egg production birds fall into three clases — high, 

 mediocre, and zero producers. The dividing line between the high and medi- 

 ocre producers came at about 30 eggs. There is great variation in the number 

 of eggs laid by birds in the over-30 class. Broodiness, age, and time at which 

 laying commences in the fall all influence the number of eggs laid. But aside 

 from these factors birds of the same age, beginning to lay at approximately the 

 same time, and which do not become broody, do not lay at the same rate. 



With regard to rhythm and very high egg production, the curve of the winter 

 egg production did not slope evenly to the base line, but formed a shoulder at 

 70 to 80 eggs. This shoulder is taken to be an indication, from a genetic stand- 

 point, of a group of individuals differing genotypically in their capacity for egg 

 producton from the remainder of the high class. The existence of this group 

 is thought to be due in part to the high-frequency pullets. 



• Various causes may interfere with the normal rhythm, such as environment, 

 season, method of management, and internal factor, as broodiness. 



It has been found that there are hens which never lay an egg, but which 

 visit the nests according to a very definite rhythm. The hours of such visits 

 fall into the same sort of rhythm as normal hens. These facts point to the 



