On Relative Growth in the Jaws of Certain Fishes.


  • A. E. Needham


  • 1In Lepidosteus osseus growth of the jaws relative to the rest of the body is of the type termed heterogonic.
  • 2There are two quite distinct periods in this growth, both showing heterogony, the growth coefficient being much higher over the first than over the second period.
  • 3The growth of the jaws relative to the rest of the body in Belone and Hemirhamphus is essentially similar to that of Lepidosteus, with the same two periods of heterogonic growth.
  • 4The difference in growth-rate between the two periods may possibly be correlated, on the one hand with differences in the histology of the growing jaws, and on the other with larval adaptation.
  • 5In certain cases, for example Hemirhamphus far and Polyodon spathula, it is conceivable that growth essentially similar in nature to the preceding examples is masked on a log/log graph by a prolonged transition period between the two phases of heterogonic growth.
  • 6In B. vulgaris both jaws show the two periods, but with considerable differences between their respective growth coefficients, producing an initial lag in the upper jaw and a later compensation.