435 



for temporarily installed incubators during the series of experiments in 

 which they were so designated). With the maximum amount of experi- 

 mental work going on, the entire alphabet was used in designating 

 chambers and places in which animals were kept; and some such plan is 

 needed for convenience of records and conversation with assistants and 

 caretakers. When once adopted, these letters were allowed to stand in 

 subsequent years for all the permanent pieces of the equipment. (For the 

 meanings of other alphabetical designations, see p. 363.) 



The records of the codling moth work were kept on the special ruled 

 paper already mentioned, the heading being proportionally filled out ; and 

 the numbers were inserted on the celluloid above the individual larvae 

 and corresponding numbers at the heads of the long columns on the 

 experimental sheet. When the observer looked over the experiments 

 morning and evening, he recorded the condition of each individual, as 

 follows : A small check indicated that the larvae were present and alive ; 

 the letter P indicated that the larvae had pupated ; E, that adults had 

 emerged; D, that larvae had died; M, that they were missing; and K, 

 that they were accidentally killed. The use of the check mark was very 

 desirable, ordinarily, to indicate that the animal was actually observed, 

 because later on, if there had been no such record kept, or if something 

 new had occurred, one might otherwise wonder whether he had actually 

 looked at it or not. The check marks avoided this form of doubt in 

 working over the results. In counting the days which elapsed from the 

 time of pupation to the time of emergence or any other period, clerks 

 were first put to work ruling the sheets into days, where the observations 

 were made twice a day, which was the case in all except the low tem- 

 peratures. They were warned especially to look out for any irregularities 

 of times when observations had been missed, as was sometimes necessary, 

 particularly with the heavy program, and in some of the lower tempera- 

 tures where little progress was made, which were ordinarily looked over 

 twice a day. These clerks drew a horizontal red line across the paper, 

 separating the days; then, starting with the data of pupation, for 

 example, they checked each corresponding reading. Thus, if the pupation 

 occurred in the forenoon, they checked each subsequent forenoon reading : 

 if in the afternoon, each subsequent afternoon reading. All readings 

 were checked to the first. At the same time, the clerks counted the 

 number of days from the time of pupation until the time of emergence, or 

 whatever other phenomenon was being observed ; and the number of days 

 which had elapsed was written at the bottom of the column or at the 

 end of the record of the particular individual. This made it possible for 

 any person to rapidly check the work of the clerks, who were found to 

 have carried out this plan with a great deal of precision, having rarely 

 made any errors. 



