66 INLAND FISHERIES. 



by the temperature, but the nature aud extent of these disturbances 

 are yet to be learned. 



From the practical point of view a great deal more depends up- 

 on the understanding- of their habits and the effect of temperature 

 and light upon them than would at first appear. Indeed, one of 

 the most serious difficulties, if not the most serious one, in the 

 rearing of the young is that of adapting the ajiparatus to the 

 peculiarities of the swdmming-habit. This subject will l^e taken 

 up again in the account of our experiments (p. 70). 



What has been said above applies to the first, second, aud third 

 stages of the young lobster. When the skin has been shed the 

 third time and the lobsters have entered the fourth stage, there 

 is immediately an almost miraculous change in their habits. In 

 many respects the difference between the fry in the third and fourth 

 stages is far greater than between animals belonging to different 

 orders, and the change may be compared to the metamorphosis of 

 flying insects from their larval to their winged condition. In the 

 lobsters, however, the direction of the change is the reverse of 

 that in the insects. The former at once become adapted to life on 

 the bottom. They tend to quit their swimming-habits, except for 

 purpose of changing their position, capturing prey, etc. They 

 crawl over the bottom, hide under shells aud sea-weed and, if 

 these objects can not be found, they even burrow in the sand. 



Not the least remarkable of the altered characteristics of the 

 fourth stage is their mental attitude. Upon entering this stage 

 they are born again, they know good and evil ; for the first time 

 the sense of fear is evident, and they retreat from danger ; there is, 

 in short, a purpose and direction in their activities which was not 

 apparent in the three earlier stages. 



It should not be inferred that they lose the power of swim- 

 ming — this is not lost for months — but the swimming is now foi* 

 the purpose of going from place to place, or for retreating from 

 danger, not merely to keep them afloat. 



A brief statement of one experiment will illustrate the sudden- 

 ness of this change of habit. Three hundred specimens recently 



