THE AMERICAN LOBSTER. 27 



shore. This is explained, lie thinks, by the current and by the rise of the tides in the 

 straits of Northumberland, which make the southern water cooler, and hence delay 

 the spawning- (,805, p. 233). 



Nielsen finds that the temperature of the water along the coast of Labrador ranges 

 very low and does not exceed 46.05° F. on the warmest summer days. The lobster is 

 thus debarred from this coast north of Henley Harbor, where it conies more directly 

 under the influence of ice and the arctic current (see p. L5). 



SENSIBILITY TO LIGHT. 



The lobster is essentially a nocturnal animal, exploring the bottom in the quest of 

 food mainly in the night, when it is far more active than during the day. This can be 

 proved by anyone who watches their habits in aquaria or in lobster ponds or cars. It 

 is tine that they show some activity in the daytime, especially if they are fed, but at 

 night they become very restless. Moving nimbly about, they explore every part of the 

 car or investigate anew the resources of the aquarium. I believe that the eggs are 

 laid and that the pairing takes place at that time, and this inference is strengthened 

 by the fact that this is the common habit of shrimp and many other Crustacea. The 

 crayfish, according to Chantran {37), usually lays its eggs in the night. 



According to Forel, light can not penetrate in the ocean below a depth of 400 meters 

 of tolerably clear water, but even in 50 fathoms off the Atlantic coast the difference 

 between day and night can not be very considerable. This is not the case in shallow 

 bays or sounds with sandy bottom, which lobsters freqneut in summer, and where we 

 may expect to find the greatest difference between their diurnal and nocturnal habits. 

 The lobster, like many other marine invertebrates, is very sensitive to the extremes of 

 heat and cold. If exposed to direct sunlight out of the water, or to the nipping air 

 of a winter's day, it weakens and succumbs in a short time. 



The large floating cars in which lobsters are generally stored alive, in readiuess 

 for market, are always kept closed. When they are particularly shallow and the 

 lobsters are exposed to the glare of the sun they always suffer and sometimes die in 

 consequence. The majority of lobsters probably spend the greater part of the year 

 in depths where the effect of sunlight is but very slight, and during the course of its 

 evolution the eye of this animal has become sensitive to a minimum quantity of light 

 For this reason alone we should expect that the adults would avoid intense sunlight 

 The effect of light upon the colors of the shell is considered in another place. (See 

 pp. 135. 136.) 



DIGGING AND BURROWING HABITS OF THE LOBSTER. 



The lobster not only digs up the sea bottom in its search for shellfish and covers 

 itself with mud in cold weather, but burrows, under some conditions at least, as 

 extensively as the muskrat. I have observed this interesting habit only in lobsters 

 confined in pounds where they are obliged to adapt themselves to new conditions, it 

 is true, but since they burrow while in these inclosures in summer as well as in winter, 

 we may infer that the habit is one which is often practiced when the animal is free to 

 roam at will. This has been observed, moreover, by fishermen who have frequently 

 taken lobsters from their holes. 



