but there is possibly a variation in other organs, such as the leg or tarsus, but it is difficult to obtain reliable measurements on some of these parts. The most vigorous nestling (No. 1) more than doubled in weight on the first day, more than trebled on the second, and more than quadrupled on the third, while on the twelfth day, when it left
Fig. 29. Young Cedarbird, No. 1 of table, shortly after hatching, lying on side, cicatrix of umbilicus showing on abdomen; weight 5 grams. August 10, 1901.
the nest it had increased its initial weight seventeen-fold. What ten days will do for the young cedarbird on the score of appearance may be seen by comparing Figs. 29 and 30, the first of which shows nestling No. 1 when about two hours old. The data on which these curves are based are given in the following table.
Fig. 30. The same Cedarbird (on left) as shown in Fig. 29, ten days later with birds Nos. 2 and 3 from the same nest. All show the crouching tendency, in evidence of fear.
Kuhlmann,The Psychological Review, Monograph Series, No. 44, November, 1909. who has recently published an interesting study of the development of the instincts and intelligence in certain altricious birds, in particular the turtle dove, the brown thrush and the red-wing blackbird, finds the rate of growth quite similar to that shown for the
