64 



INLAND FISHERIES. 



2. 

 3. 

 4. 



5. 



6. 



7. 



8. 



9. 

 10. 

 11. 



It is not ]iossil)le to say at present that the variations in the 

 length of the early stages are due entirely to the difference in 

 temperature, and it may be that other factors have more or less 

 influence ; but it is extremely probable that temperature is the 

 main factor. In other animals the increase of temperature is 

 known to have an accelerating effect on the development, e. g., 

 in the development of the eggs of one of the marine worms, Lepi- 

 donoius, the development could be increased to three times its 

 usual rate by warming the water. 



The ])roportion of time spent in the first, second, and third 

 stages was, at Wickford, approximately equal (see table, page 

 78), l)ut the record is not complete enough to allow very accurate 

 statements as to the exact amount of time spent in each stage. 



From the standpoint of lol)ster-culture there are advantages in 

 making the duration of the critical period as short as possible, 

 besides the saving of extra labor. The especial dangers to which 

 the young are exposed from their enemies and from physical 

 environment are materially increased when the fry develop 

 slowly, so that the sooner they reach the fourth stage the less 

 they need be exposed. Among the enemies must be recorded in 

 this connection the vegetable growths of various kinds which find 



