198 REPORT OF COMMISSIONERS OF INLAND FISHERIES. 



present purpose we may conceive of normal behavior as that type of 

 action which is present when the response to exaggerated or unusual 

 conditions of stimulation is at its minimum. In view of the fact that 

 swimming constitutes the chief activity of the larval lobsters, our 

 question resolves itself into the following: What is the nature of the 

 normal sivimming? 



When one first observes the behavior of individual larvse among 

 the thousands contained in the large hatching bags, no difference is 

 evident in the swimming of those in the first three stages. In all 

 instances the back of the larva is, for the most part, uppermost, the 

 abdomen bent under and downward at an angle of about 60 degrees 

 from the longitudinal axis of the cephalo-thorax, which in turn is 

 inclined at about 30 degrees from the horizontal plane. In daylight 

 this position may occasionally be maintained without modification 

 for several minutes, but the equilibrium is frequently disturbed by 

 other body movements, which, upon superficial observation, appear 

 to be of a most diverse and ill-ordered nature. There are leanings, 

 turnings, fallings, somersaults, revolutions, and rotations, which 

 follow one another in no apparently definite sequence,, and which 

 disturb the general equilibrium either greatly or slightly as the case 

 may be. 



Whether the balanced equilibrium, the devious rotations, or other 

 activities, be in effect, the exropodites, or swimming attachments of 

 the thoracic appendages, beat the water more or less constantly with 

 short vibratory strokes, sometimes lifting the larvse high, toward the 

 surface, and again allowing them to sink to the bottom where they 

 may frequently lie for some moments almost motionless, only to 

 resume again immediately their varied activity. Now they swim 

 forward, now backward, now they lurch to the side, now to the rear, 

 always maintaining more or less energetically this series of apparently 

 aimless activities. Such is the nature of the swimming in daylight 

 or other brilliant illumination; and for our purpose it can not be 

 called the normal swimming of the lobster larvse. It is only under 

 special conditions that the latter may be observed; and, in view of 



