. Ciba Foundation colloquia on ageing. Old age; Aging; Animals -- growth & development. Physiological Approach in Study of Ageing 21 The situation is quite different in lower vertebrates. The fertility of the females does not generally lessen with age, and the longer and older the female, the greater is its capacity to produce eggs—at least up to a certain age. In snakes, for instance, fertility increases with the age of the mother. In the Matrix natrix we have studied in our laboratory, the clutch 240 220 200 180 160 140 120 o q 100 o CL 80 o o 60 40 20. 10 II I 2 3 4 5 6 7 8 AGE OF HEN (
. Ciba Foundation colloquia on ageing. Old age; Aging; Animals -- growth & development. Physiological Approach in Study of Ageing 21 The situation is quite different in lower vertebrates. The fertility of the females does not generally lessen with age, and the longer and older the female, the greater is its capacity to produce eggs—at least up to a certain age. In snakes, for instance, fertility increases with the age of the mother. In the Matrix natrix we have studied in our laboratory, the clutch 240 220 200 180 160 140 120 o q 100 o CL 80 o o 60 40 20. 10 II I 2 3 4 5 6 7 8 AGE OF HEN (vears) Fig. 1. The variation with age of egg production in three strains of domestic fowl. (After Romanoff and Romanoff, 1949.) size varies with age from 16 to 51 eggs per clutch (Fig. 2). Another species, Coronella laevis, shows the same trend (from 4 to 13 young per brood in that viviparous snake). A senile decrease in fertility can nevertheless be noted in the oldest individuals, as shown by Klauber's (1936) data, but it takes place at a much later age than in warm-blooded verte- brates of similar size (Fig. 3). In fishes the situation appears to be quite similar. To take a single example, the average egg. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Ciba Foundation; Wolstenholme, G. E. W. (Gordon Ethelbert Ward). Boston, Little, Brown
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