In the hamster thyroid gland, the sphincter apparatus divisible into the complete and incomplete ring forms is found at the branching point of the arteries and projects toward the cavity of the mother artery.
The complete ring form indicates a complete arrangement of smooth muscle fibers, and the incomplete ring form shows a discontinuous arrangement and appears as paired cristae which are almost parallel to the axis of the mother artery. The former form is found generally at a point where a branch runs at a right angle from the mother artery, while the latter form is seen at another point where a branch begins at an acute angle. Both forms begin to appear in the capsular zone from the 2nd day after birth and later occur in the central zone of the gland also.
The apparatus may play an important role in regulating the blood supply in the thyroid gland.

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Besides peroxidase staining, several peculiar stainings of erythrocytes including supravital staining have been tested on 114 cases of 25 different animals as well as 23 cases of human bone marrow bloods, the following results being obtained:
1) The nuclei of erythroblasts in human bone marrow were stained green or greenish brown with the orthophenylenediamine reac- tion (peroxidase staining).
2) In animals, erythrocyte nuclei of urodele amphibian (Triturus pyrrhogaster and Onychodactylus japonicus) indicated the most intensely positive orthophenylenediamine reaction. On the other hand, the ery- throcyte nuclei of anuran amphibian indicated a weaker reaction, while those of birds, reptiles and of fishes remained reaction negative in general. This reaction was tested only on mature erythrocytes in the blood floor of submammalian group.
3) It was shown that a peculiar rod-like structure appears in the nuclei of amphibian erythrocytes with the fixation by drying in the air, formaldehyde gas, ethylalcohol, acetic acid as well as with the parafuchsin staining. This structure is thought to be an artifact and caused by the coagulation of chromatin, indicating one of characteristics of the amphibian, especially urodele amphibian. This staining method is called FAP method from the capitals of Formaldehyde-Alcohol-Parafuchsin. The erythrocyte nuclei of birds, reptiles and fishes did not show rod-like structure by this FAP method.
4) It is thought that these two characteristics of erythrocyte nuclei of urodele amphibian, namely, positive orthophenylenediamine reaction and distinct rod-like structure, have relationships with the high concentration of DNA as well as the enormously large size of them.
5) In the supravital staining with janus green B as well as with victoria blue 4R, mature erythrocytes of fishes, urodeles, anurans, and reptiles, furthermore human erythroblasts demonstrated peculiar mitochondria. The shape of these mitochondria was classified into five types. Among these, urodeles demonstrated the most peculiar type. Victoria blue 4R was inferior to janus green B in the supravital staining of erythrocytes.
6) The staining ability of erythrocyte nuclei with various basic dyes, was varied according to the animal species. Newt and some fishes indicated the most intense color, reptiles the medium-intense, while toads the weakest. The parallelism between the DNA content and this staining intensity of erythrocyte nuclei was admitted to some extent.
7) Nucleated erythrocytes could be seen in the blood floor of some mammals in the absence of disease although in very small numbers. The examples of these mammals, including those heretofore reported, were monkey, sheep, dog, cat, pig, llama, camel, bat, hedge- hog, rabbit, guinea pig, albino rat, mouse, opossum and golden hamster.
8) It was revealed that the orthophenylenediamine reaction as well as the FAP method were valuable for the comparison of nucleated erythrocytes of submammalian vertebrates.

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