REPORT OF COMMISSIONERS OF INLAND FISHERIES. 199 



the fact that it is the conditions of Hght which influence, more 

 strongly than any other factors, the behavior of the larva^, it is under 

 certain light conditions that we may expect to find manifested what 

 we may call the characteristic or normal swimming. 



It is the twilight, or nocturnal, swimming of the larval lobsters 

 which invariably presents the fairest example of natural behavior. 

 It is at such times alone, or when the larvae are submitted to arti- 

 ficially produced twilight, that the multiplicity of conflicting cross- 

 light influences are most nearly eliminated from the amphitheatre; 

 and whatever sort of swimming or other reactions are then mani- 

 fested can be said to represent most truly and most exclusively those 

 influences which arise from the physiological states themselves, 

 independent of stimulation from without. In many instances, when 

 the twilight was so dim that the activities of the larvse could with 

 difficulty be discerned, the writer "has observed that the swimming 

 was delicate and regular. The young larvae would mount up, bird- 

 like, to the surface water, and often hover for many seconds in a 

 single position, or swim backward or forward with equal ease — 

 perfect masters of their own activity. In case, at such times, even 

 a lighted match should be brought near the side of the jar in which 

 the larvae were confined, the same restless and uncertain swimming, 

 characteristic of the diurnal activities, would again be manifested, 

 with the accompanying leanings and rotations. From these facts 

 we may assume that the twilight swimming of the larvae probably 

 represents most accurately the natural behavior; and that the 

 peculiar antics, characteristic of the daylight swimming, represent 

 an unusual type of behavior, due to the action of conflicting external 

 stimuli. 



The question now naturally arises, do the various turnings and 

 rotations, leanings, and fallings, which constitute the apparent hap- 

 hazard behavior of the larval lobsters swimming in daylight or other 

 brilliant illumination, give any indication of a method which may 

 underlie this seemingly random activity? Our previous observa- 

 tions have at least given us a suggestion as to a means whereby we 



