AGEING OF THE EGG AND DEVELOPMENT 



127 



The data should be complete and arranged in tabular form, but the final results should be 

 indicated in the form of two graphs, one for the 20 C. eggs and another for the 10°C. 

 eggs. Photographs, drawings, and cytological sections are very instructive. 



TEMPERATURE 



10 eggs 



DAYS 

 6 7 



10 11 12 



(Indicate data in percentages of total eggs for cleavages; but in 

 percentage of cleaving eggs for gastrulae and neurulae^ ) 



100- 

 75- 

 50 

 25 



J L 



2 3 4 5 6 

 DAYS - AT 10°C. 



100- 



75- 

 50- 

 25- 



J L 



10 12 14 



DAYS - AT 20"C. 



CLEAVAGE PERCENTAGE OF AGED EGGS 



REFERENCES 



BLANDAU, R. J. G W. C. YOUNG, 1939 - "The effects of delayed fertilization on the development of the Guinea Pig ovum." 



Am. Jour. Anat. 64: 

 BRIGGS, R. W. , 1941 - "The development of abnormal growths in Rana pipiens embryos following delayed fertilization. " Anat. 



Rec. 81:121. 

 DALCQ, A. M. , 1938 - "Form and Causality in Early Development. " Cambridge Univ. Press. 

 HERTWIG, R. , 1925 - "Uber experimentelle Geschlechtsbestimmung bei Froschen. " Sitzber. der math, -natur. Abt. der Bayer. 



Akad. der Wiss. Jahrgang, 1925. 

 HOLTFRETER, J., 1943 - "Properties and functions of the surface coat in Amphibian embryos. " Jour. Exp. Zool. 93:251. 

 LEHMANN, F. , 1937 - "Die Wirkung chemischer Factoren in die Embryonalentwicklung. " Rev. Suisse de Zool. 44:1. 

 WITSCHI, E., 1921 - "Development of the gonads and transformation of sex in the frog. " Am. Naturalist, 55. 

 WITSCHI, E. , 1934 - "Appearance of accessory 'Organizers' in over ripe eggs of the frog. " Proc. Soc. Exp. Biol. G Med. 



31:419. 

 ZIMMERMAN, L. & R RUGH, 1941 - "Effect of age on the development of the egg of the leopard frog, Rana pipiens." Jour. 



Morph. 68:329. 

 ZORZOLI, A. & R. RUGH, 1941 - "Parthenogenetic stimulation of aged Anuran eggs. " Proc. Soc. Exp. Biol. & Med. 47:166. 



