290 ^Journal of Comparative Neurology and Psychology. 



machines the nature of whose operations can seldom be predicted 

 unless the age, the stage, the kind and degree of the stimulus, are 

 accurately known. These conditions of reaction indicate the 

 extent to which the behavior of young lobsters is determined by 

 their physiological states; and the foregoing experiments show in 

 what way these physiological states change, not only from one 

 stage-period to another, but even during the same stage-period, 

 through the influences of metabolism, development, and perhaps 

 still other factors. The extent to which the natural behavior of 

 animals in their natural environment can be explained on the basis 

 of the results of laboratory experiments depends largely upon the 

 animal and the kind of reactions involved. It is quite probable 

 that some of the characteristics of reaction, which have been de- 

 scribed in the present paper, determine in a large measure, the daily 

 behavior of the larval and early adolescent lobsters when they are 

 in their natural environment. Unfortunately, however, we know 

 too little regarding the behavior of lobsters under natural condi- 

 tions, to attach great importance to far-reaching explanations of 

 their daily activities on the basis of laboratory experiments. A 

 few points, however, may be noted. The reports of biological 

 surveys make it clear that, at the surface of the ocean or of bays 

 in which lobsters are known to live and breed, the stage most often 

 taken in the tow-nets is the fourth; the larval stages are much less 

 frequently found, the fifth stage seldom, and later stages never. 

 Observations which were made on lobsters of different stages 

 taken from the Wickford hatchery and liberated in the surround- 

 ing waters of Narragansett Bay yield similar evidence regarding 

 the immediate natural distribution. In these cases the lobsters 

 of the larval stages were found to swim for a brief time, then grad- 

 ually disappear from the surface; the fourth stage lobsters swam 

 actively at the surface so long as they were observed; while the 

 fifth and all later stages plunged at once into the deeper water and 

 were immediately lost to sight. 



As the wTiter has already suggested, it is impracticable to 

 attempt to explain the natural behavior of larvae of the first three 

 stages, on the basis of the reactions which have been discussed 

 at some length in the present paper. The light (depending upon 

 its intensity and directive influence; and upon the age, stage, and 

 previous condition of the larvae) may determine at one time a posi- 

 tive, at another a negative, response, so that the general reaction 



