Among five species of Pacific salmon; Oncorhynchus masou, O. nerka, O. tschawytscha O. keta and O. gorbuscha were compared, i. e., the relative position and the arrangement of vomerine and palatine tooth bands in the roof of the mouth, and the form of these tooth bands, teeth and labial fold as taxonomic characters.
As a result, the above-mentioned characters turned out to be useful for the determination of each species. The main differences between the species are shown in Fig. 1 and Table 2.
O. nerka and O. tschawytscha show wide differences in the position and the form of palatine tooth band from other species. O. masou and O. keta show wide differences in the position and the form of vomerine tooth band. In O. gorbuscha, the tip of its vomerine tooth band more projects beyond palatine tooth band than other species, from one-third to one-fourth in length of vomerine tooth band.
Individual variation of these taxonomic characters, in the roof of the mouth, were not found.

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When the egg of Alaska pollack, Theragra chalcogramma attains to actual maturity, it decreases in specific gravity and floats in the sea water, whereas the specific gravity of immature egg is smaller than that of the ordinary sea water. Consequently, it may be admissible to consider that the eggs which sink in sea water immediately after discharge are not yet fully matured, i. e. that they are immatured eggs having no capacity for normal fertilization.
Fertilized or developing eggs float at least till the hatching stage, because, upon fertization, they have gained a resistance against the hypertonicity of the surrounding sea water. The unfertilized niature egg is parthenogenetically activated without insemi-nation when it comes in contact with sea water, undergoing the same changes as the fertilized though formed blastodisc does not begin to be divided, and it gains a resistance against the hypertonicity of the surrounding medium ; accordingly it can remein for some time floating in the activated state in sea water. But such an egg begins to sink afterwards from loss of resistance to hypertonicity because of the lowering of its vitality. That is, the diffusing out of water from egg interior occurs and increase of specific gravity of the egg results.
Egg-activation and development are much affected by the salt concentration of the medium and it may be considered that isotonic and also hypotonic sea water are unsuitable media for activation and development of the egg.

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1. Material and Method
The materals used are the teeth of the upper and lower jaws, palatine, vomer, tongue and pharynx of Scombrops boops (H_OURRUVN), measuring 10-20 cm in total length. The same method as before has been adopted.
2. External features.
The alveolar parts of the jaws and palatines consist of inner and outer bony plates. The teeth are either inserted between these plates or attached to either of the two. The teeth of the jaws stand in a row, and the palatine teeth are in two rows. These teeth are all elongated cones. The vomerine, lingual and pharyngeal teeth are very small and swarm in the form of villiform teeth. They curve inwards and backwards.
3. Microscopic Findings.
With the exception of the villiform teeth of which the presence of enamel is doubtful, all the teeth consist of enamal and dentin.
The enamel is of homogenous structure, and covers one half or one-third from the apex of a tooth.
The dentin of this fish is identical with the osteodentin described by C. S. TOMES in his study of the pike, and includes what R. OWEN called medullary canal.
These teeth when fully developed, are anchylosed to the bones.

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