Temperature as a factor in the determination of sex in amphibians / Helen Dean King.

  • Helen Dean King
Date:
1910
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Licence: In copyright

Credit: Temperature as a factor in the determination of sex in amphibians / Helen Dean King. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    individuals whose sex I have ascertained during the course of the experiments which I have made to study the problem of sex- determination in this form. No very definite conclusions can be drawn from the results of the experiments summarized in Table I. The percentage of females obtained from the lot of eggs that was fertilized at a temperature of 26° C., although higher than the probable average for the species, is still within the limits of pos- sible normal variation in the proportion of females developing from eggs laid by different individuals. A relatively low per- centage of females developed from the lot of eggs that was fertilized at 90 C., yet this percentage is about the same as that obtained in one of the series of experiments made to ascertain the influence of nutrition on the determination of sex in Bufo (King, 4). It may be possible to explain the results obtained in this last series of experiments, as well as those of the first series of temperature experiments briefly described above, as due to the fact that occasionally a batch of eggs gives an unusually low or an unusually high percentage of females and that by chance such exceptional lots of eggs were used for these experiments. As this last series of experiments was carried out it is open to serious criticism. The eggs that were fertilized in warm water were laid by one female, while those that were fertilized in the cold water were laid by another individual. This gives an op- portunity for the results to be influenced by possible normal variations in the sex-ratios of different lots of eggs. The two sets of eggs were fertilized by sperm from different males also and, as Morgan (8) has pointed out, there is the possibility that the male is responsible for the determination of sex in amphibians. In order to avoid all obvious sources of error and, if possible, to obtain results that would give definite conclusions, another series of experiments was made this past spring with the eggs of Bufo. On April 7, 1909, a female which had just begun to lay was killed by pithing and the eggs removed to a dish of fresh water. Lots of about 350 eggs each were artificially fertilized in water which was kept at given temperatures (350 C., 30° C., 20° C., io° C., 5 0 C.) for twenty minutes and then allowed to come gradually to the room temperature (180 C.). In all cases sperm from the same male was used. The extreme temperatures at
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