This report describes the results of the experiments made for research (B) mentioned in Report 1.Ⅰn monomyaria, it is desirable from the viewpoint of dynamics that the adductor muscle is situated on the perpendicular bisector line of ligament far apart from the ligament The author investigated on Ostrea denselamellosa Lischke whether the rational re1ation above mentioned was actually recognizable, and found the fact that the mechanical actions of adductor and ligament are eqllally effectual in closing and opening the valves. (For the determination of the position of adductor, the center of the gravity of the shell was chosen as a standpoint because it was Settled on a definite part of the shell. 1.The center of the gravity of the shell is situated on or near the perpendicular bisector of the ligament. 2.Roughly speaking, it may be said that the center of the gravity of the shell is situated about half the way from the ligament to the inner margin. 3. The lower margin of the adductor muscle is tangent to,or near, the center of gravity. 4. The Center of the muscle is situated on the left side and apart 5.76/100 distant from the line which passes the center of gravity on the way from the center of the ligament to the inner margin.
開閉殻運動を力学的に見る時二通りの考え方のあることは第2報に於て述べた如くであるが,本報以下に於ては残る(2)の問題に就て研究した結果を報告する.先づ単柱類の開殻筋に就て考えると,開閉殻運動を合理的に行う為には閉殻筋は出来る丈靱帯に対して垂直方向にあり,叉殻の中央に近く且つ靱帯から成る可く遠い位置にあることが望ましい. 然し此のような目的を以て閉殻筋の位置に就て論じた報告は未だ見当らず,唯DowningがAnadonta grandis Say を用いその前後両閉殻筋の位置を生物測定学上の目的を以て測定しているのみである.著者はイタボガキに就て実際どの程度此の力学的合理性を満足しているかを調査したのであるが,靱帯及び閉殻筋は共に合理的に作用し得るように夫々配置されていることを認めたので以下之に就て報告する.