抄録
The writer examined for the similar purpose with that of his previous study(1) the digestive tract and its contents of adult forms of two kinds of flat-fishes, viz., Lepidopsetta mochigarei (J. N., Kôri-mochigarei) and Hippoglossoides elassodon (J. N., Uma-garei), both of which were collected from many localities of the North Pacific, as are shown in the Table 2 and 3.
The forms of their alimentary tracts show remarkable resemblance with each other; they have similarly the sac-shaped stomach furnished with valves at the pars cardiaca and pars pylorica, four pyloric appendages, the vortical intestine, the liver of moderate size, the gall bladder and the distinct pancreas. So, it is quite impossible to perceive the morphological difference of alimentary tract between the two fishes. Nevertheless, it is highly interesting that there are some differences in the form of their mouthes and the teeth. The former species has the small mouth in which one row of minute, blunt teeth develops on each jaw of the left side only, teeth on jaws of the right side are degenerated. The latter species has the large, oblique mouth in which one-row of minute but rather sharp teeth is present on each jaw of both sides. In both species, the mouth cleft of the left side (lower side) is always larger than that of the right side. Such structure of the mouth and the development of the teeth on jaws would be regarded as an ingenious adaptation to the mode of their feeding habit. The former species feeds mainly on small sluggish animals on or in the sandy bottom, such as isopods, amphipods, shell-fishes, ophiurans and sand-living worms, while the latter species feeds not only on the said animals but also rather active creatures living on or above sea-bottom such as small shrimps
