1910] 



(lira nit. Periods of Embryonic Development. 



17 



As regards the first and second. Two eggs of the same 

 parentage deposited simultaneously (within 15 seconds of each 

 other) hatched 12 r 2 hours apart; 8 esrzs from the same parent 

 deposited in 5 minutes, hatched within an hour of each other; 

 the 2 eggs of the first lot deposited 4 minutes later than the 8 

 eggs of the second lot, hatched" 12 hours earlier (mean time) ; that 

 is, the period of embryonic development was a half day shorter. 

 Again, 54 eggs deposited in 30 minutes hatched during a period 

 of 31 hours; 158 eggs deposited in 120 minutes hatched during a 

 period of 19 hours; the 158 eggs of the second lot deposited 4^ 

 hours later than the 54 eggs of the first, hatched 14 hours later, 

 hatching commencing, however, 24 hours later than the com- 

 mencement of hatching in the first lot. 



The comparative durations of the period of embryonic develop- 

 ment, with related data, are shown in Table I. 



Table I. Comparative Durations of the Egg Stage in Similar Lots of 

 Eggs Deposited in Rapid Succession, Sannina exitiosa Say. 



s Deposition of first and last egg. The combined lots were deposited in 

 362 minutes and hatched during a period of 43 hours with an egg stage of 

 8.29 days. i Mean. 



