Retention of normal polarity in centrifuged stems of Tubularia.

Stems of the hydroid, Tubularia crocea, were cut from the colony, which had been taken directly from the sea. The hydranths were removed by cutting them from the stems immediately below their attachment. A small branch from the stem was left intact to serve for orientation, and the hydranth which belonged to this branch was cut off.

These stems were placed in specially prepared tubes fitted to a hematocrit centrifuge, operated by hand. Rotation was made at varying speeds and for varying intervals of time ranging from a minimum speed of rotation of about two hundred and forty per minute to a maximum of about six hundred rotations per minute. A greater speed than this resulted in forcing the contents of the perisarc tube out at the distal end. The periods of time of rotation varied from a minimum at highest speed of one minute to a period of maximum operation at medium number of rotations per minute (approximately three hundred, the centrifuge being about one-in-four, but there was no speedometer available to accurately measure the number of rotations at the higher speeds), for one half hour.