13 



Before 2 P.M. small no, of eggs laid after 90 minutes darken 



ing. 



2-3 P.M. almost the nox'mal n-omber laid 90 minutes darkening 



3 - 4 " " " " 65 " " 



4 _ 5 " " •' " 60 " " 



5 - 6 " " " " 60 " " 



6 - 7 " " " " 50 " " 



At 8 P.M. eggs laid normally, without darkening ar- 

 tificially. 



As the hour approached the normal time for the de- 

 position of the eggs the precision with which they wore dis- 

 charged became more and more marked. Between four and seven 

 P.M. the time of darkening necessary to produce spawning va- 

 ries not more than four minutes on either side of the hour. 



Some experiments were tried with a view to inhibit- 

 ing normal deposition of eggs, or at least of hindering it, 

 by keeping the eggs under strong artificial illiuninat ion. 

 The results were not conclusive, as the electric lights in 

 the laboratory were not in use until after dusk, when part 

 of the stimulus had already been received. The experiments 

 showed a certain amount of retarding of the process of spawn- 

 ing as a result of strong illumination. It woixld be inter- 



