The Paneth's Cells are special Gland Cells that lie at the bottom of the glands of Lieberkühn in the small intestine of some kinds of mammalia, and that have the peculiarity of containing refractive gross Secret Granules in their Cytoplasma. With reference to the shape of the Secret Granules of the Paneth's Cells, many savants (Paneth, Klein, Trautemann, Kull, & Tang etc., ) conclude it spherical, but others such as Nicolas, Möller, Tang, acknowledge that semi-spherical and irregular-shaped Secret Granules exist besides spherical ones. According to the theory of Nicolas, Paneth, Möller, & Kull, large Granules are the growth and swelling of small ones, and also Möller, Miran, Chuma state that Granules melt down, and form large homogeneous lump. But as to its Transitional Form, any detailed statements are not yet made. This is the reason that has made it the subject of my investigations. I adopted, as the material of my above study, chiefly the small intestine of the Mouse, and also of Man, Monkey, Rabbit, Guinea pig and Rat. As the results of the experimental study, I have reached the following conclusions: - 1. Most of the Secret Granules of the Paneth's Cells are homogenous spherical and similar-spherical in shape, but still very often irregular shaped Granules are found. 2. There is each Transitional Form between middle-large or large Secret Granules of net-meshes that is very often noticed, and a series of several small Granules, and also among large homogeneous Granules: namely, the growth of Secret Granules is not only due to the growth of small Granules themselves, but also to the congregation of small many Granules. 3. Secret Granules are to be considered, as Möller, and Trautemann concludes, that they are evacuated in the Glandspace in forms of Granules, and then liquefy and disappear.