The structure and some physical properties of the testudinian eggshell.
*Mr. J. D. Young, a research student, was carrying out this investigation in the Zoology Department, University College, London, during 1938 and 1939. In 1940 he joined His Majesty's Forces and was killed during the capture of Singapore. His incomplete manuscript has been edited by Dr. P. Ford.
- 1A revised account of the structure of the fowl's egg is given. It has been found that the layer previously described as amorphous (von Nathusius, 1861) and as composed of small interlaced calcite crystals by Stewart (1934), consists in fact of very large calcite crystals which enclose the ovo-keratin foundation of the shell. It is also found that the shell exhibits no sphaerulite structure whatever.
- 2The structure of the eggshell of four species of tortoise is described.
- 3The inorganic part of these shells is composed of sphaerulites of aragonite.
- 4The presence of pores in the fowl's egg is demonstrated by two different techniques.
- 5Pores are absent from the eggs of Testudo graeca and T. radiata. They appear to be present in the shells of Emys orbicularis and Amyda euphratica.
- 6Rate of water loss is both absolutely and per unit of area less from the intact tortoise egg than from the intact fowl's egg.
- 7These findings are discussed in relation to the mode of life of tortoises.