Geotropic Creeping of Young

The geotropic conduct of young rats has been discussed in a previous paper (Crozier and Pincus, 1926-27) with special reference to the angle of orientation upon an inclined plane. It was found that the angle of orientation (0) is directly proportional to the logarithm of the gravitational component (g sin ~) in the creeping plane. This is explicable as the result of the distribution of the pull of the animal's weight upon the legs of the two sides of the body during progression, upward orientation being the result of the "pull" of the legs on one side and the upward "push" of the legs on the other side; when orientation is attained, the ratio of the tensions on the legs of the opposite sides is regarded as constant and thc difference between these tensions as a constant fraction of the total downward pull. To examine further the nature of the geotropic conduct of young rats, observations on the speed of upward creeping were undertaken. Cole (1925-27) has discussed similar observations on Helix; he concludes that the speed of movement, after orientation has been attained, varies as sin a. But, as has been pointed out already (Crozier and Pincus, 1926-27), in these experiments the speed measured was that of vertical ascension, and no correction was made for the changes of 0 at the different angles of inclination; such changes occur in the orientation of gasteropods. Since, at lower angles of inclination of a creepLug plane (15°-70 °) the animal moves at an angle (0), it is necessary to multiply the time of upward creeping by the sine of the angle of orientation (0) in order that the amount of time actually necessary to cover a constant distance may bc dealt with at each angle of inclination (el. Fig. i). In terms of Fig. i, the rate of creeping is given by the