Up to the present time, only a few works are available on the structure and formation process of ascaris egg-shell. Zawadowsky (1929), as the result of his detailed investigation, revealed that the egg-shell of
Ascaris megalocephala consists of five layers. Ida (1929) reported that he could recognize four layers on the egg-shell of
A. lumbricoides and
A. suilla by various chemical treatments of the eggs. On
A. lumbricoides ova, chemical properties of the shell were studied by Chitwood (1938) who found chitosan in its “shell proper”. The “shell proper”, he called, was considered to be the whole shell layers except the protein coat. Details on the shell structure were not described in his report. Ohuchi (1951) observed the effects of acids and alkalies on the protein coat of
A. lumbricoides ova and recognized the swelling of the eggs by immersing them in inorganic acids and called this phenomena “intra-egg-shell swelling”. But no report has so far been published on the formation process of the egg-shell. In a previous paper, the present author and co-worker (1952) reported on the granules in the cytoplasm of oöcytes, which formed the 3rd layer of the ascaris egg-shell. But in that report, the formation of the 1st and thick 2nd layer of the shell, especially that of the so-called inner vitelline membrane formed just beneath the 3rd one, was not dealt with.
In the present work, the author confirmed the structural elements of the shell by means of acid and alkali treatments and observed, furthermore, its formation process in
A. suilla ova.
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