Abstract: Method of growing molluscs, such as oysters, which method comprises placing a bed of discrete oysters in a vessel through which a stream of a culture medium is caused to flow upwardly and wherein the flow rate is sufficient to maintain the oysters in suspension without causing turbulent movement in the bed.

Abstract: Method of growing molluscs, such as oysters, which comprises inducing larvae to settle on small particles of cultch and subsequently maintaining the particles of cultch with spat attached in suspension in a liquid growing medium until they have reached the size appropriate for them to be used as seed molluscs.

Abstract: An instantly variable constant current control is interposed between a bank of batteries and a motor. The variable constant current control comprises a series pass transistor operating in a linear mode and controlled by a reference voltage from a potentiometer coupled to an accelerator pedal. Correction voltage from the series pass transistor circuit is proportional to current. The accelerator reference voltage and the current correction voltage are compared in a linear operational amplifier which controls the "on" resistance of the series pass transistor.

Abstract: An arrangement of electric motors which are coupled together both mechanically and electrically comprises series pass elements and current sensing devices in the power circuits of the respective motors, each current sensing device having an output voltage which is proportional to its motor current, and which is applied to a respective linear operational amplifier having an output which controls the equivalent resistance of the series pass element (and thereby the magnitude of motor current). A single reference voltage is applied to all the linear operational amplifiers, so that, for example, if the motors are similar, each will transmit the same torque regardless of any difference in its internal impedance.