204 REPORT OF COMMISSIONERS OF INLAND FISHERIES. 



shores. To these differences is to be attributed the greater depletion 

 of lobsters observable in the southern New England fishing grounds. 

 In consideration of these facts it is not difficult to see the need of such 

 means of artificial propagation as has been instituted and carried on 

 so successfully by Dr. A. D. Mead of the Rhode Island Commission 

 of Inland Fisheries. 



XV. The Influence of Light. 



Another point which must be touched upon is the influence of light 

 upon the rapidity of development. The lobster is naturally a noc- 

 turnal animal, or at least he is an individual whose habits of life 

 seldom lead him out of the twilight or darkness of his natural haunts. 

 In captivity, at least, it appears that he is most active after dark. 

 He naturally dwells in the cracks and crevices of the most rockv 

 shores, seldom venturing forth except in search of food, which, when 

 found nearby, will be dragged back into the retreat and there de- 

 voured. The stronger the light, the more cautious and seclusive 

 becomes the lobster; and we have observed many cases of adolescent 

 lobsters which would not, though in an apparently famished con- 

 dition, take a morsel of clam while in the bright sunlight. That a 

 strong light must exercise a disagreeable effect upon them is evinced 

 (in all stages after the fourth) by their efforts to retreat from its rays. 

 During exposure they wander ner\'0usly about their cars \mtil they 

 find a dark spot, when they at once cease their activity and remain 

 quiet so long as undisturbed.* The presence of a stimulus which is 

 able to produce such definite reactions as does light can not fail to 

 be of decided advantage or disadvantage to the animal concerned. 

 In consideration of these facts, believing that the intense midday 

 light of midsummer must be disadvantageous to the young lobsters, 

 covers w^ere provided for all the cars in which experiments were being 



*This subject of light influence upon the young lobsters has been treated more fully in 

 special article, "Observations upon Some Influences of Light on the Larval and Early Adoles- 

 cent Stages of the American Lobster," which will be found later on in this report, page 230, 

 Hadley ('06): and also in an article in Science, Hadley ("05). 



