1910] 



Girault, Periods of Embryonic Development. 



13 



and a record made of the eggs deposited by her. Oviposition 

 began immediately and at timed intervals the female was 

 removed to other, clean vials and a record thus made of the 

 actual time of deposition of several lots of eggs all of the same 

 origin and deposited at successive short intervals of time varying 

 from 4 to 68 minutes. The period of hatching was then 

 recorded for each lot, showing marked variation both in the 

 cases of the individuals of any single lot and between the lots 

 themselves. The observations are not detailed enough to give 

 the actual frequency of hatching but the curves of distribution 

 shown later represent approximately what took place in each lot. 

 The whole period of time for deposition was 6.03 hours ; that 

 for hatching, 43 hours. 



The following lots were obtained and observed ; they were 

 all kept together under optimum conditions, there being no violent 



h 1 ('A. x 



Figure 1. — 54 observations. 



The tendency of hatching here 

 is roughly expressed by the 2 

 modes. 



i 1>2 i 



/2 



Fig-ure 2. — 45 observations. 



The tendency is practically the 

 same as in Lot No. I. 



changes in temperature. The variation described therefore is 

 apparently usual or normal. 



Lot. No. I. Fifty-four eggs deposited in rapid succession during a 

 period of 30 minutes (10:38 to 11:08 a. m.) began to hatch at 11 p. m., 

 August 31st; after 9% hours (8:30 a. m.) but 24 (44%) had hatched; 

 after 12 hours (11 a. m.) but 32 (59%) had hatched and none hatched 

 during the next 7 hours (to 6 P. M.) ; however, the remaining 22 eggs 

 (41%) hatched during the next 13 hours. The period of hatching 

 extended to 31 hours or 30y 2 hours over the period of deposition. The 

 curve of distribution would be something like that shown in figure 1. 



Lot No. II. Forty-five eggs deposited similarly in the same period 

 of time (11:10 to 11:40 a. m.) began to hatch at about the same time 

 as in the preceding lot. After 9% hours but 6 (13.3%) had hatched; 



